io-bmp.c 38.8 KB
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/* -*- mode: C; c-file-style: "linux" -*- */
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/* GdkPixbuf library - Windows Bitmap image loader
 *
 * Copyright (C) 1999 The Free Software Foundation
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 *
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 * Authors: Arjan van de Ven <arjan@fenrus.demon.nl>
 *          Federico Mena-Quintero <federico@gimp.org>
 *
 * Based on io-ras.c
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 *
 * This library is free software; you can redistribute it and/or
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 * modify it under the terms of the GNU Lesser General Public
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 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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 * Lesser General Public License for more details.
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 *
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 * You should have received a copy of the GNU Lesser General Public
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 * License along with this library; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
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 */

#include <config.h>
#include <stdio.h>
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#ifdef HAVE_UNISTD_H
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#include <unistd.h>
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#endif
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#include <string.h>
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#include "gdk-pixbuf-private.h"
#include "gdk-pixbuf-io.h"
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#define DUMPBIH 0
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#if 0
/* If these structures were unpacked, they would define the two headers of the
 * BMP file.  After them comes the palette, and then the image data.
 *
 * We do not use these structures; we just keep them here for reference.
 */
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struct BitmapFileHeader {
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	guint16 magic;
	guint32 file_size;
	guint32 reserved;
	guint32 data_offset;
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};

struct BitmapInfoHeader {
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	guint32 header_size;
	guint32 width;
	guint32 height;
	guint16 planes;
	guint16 bpp;
	guint32 compression;
	guint32 data_size;
	guint32 x_ppm;
	guint32 y_ppm;
	guint32 n_colors;
	guint32 n_important_colors;
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};
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#endif
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/* Compression values */
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#define BI_RGB 0
#define BI_RLE8 1
#define BI_RLE4 2
#define BI_BITFIELDS 3

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/* State machine */
typedef enum {
	READ_STATE_HEADERS,	/* Reading the bitmap file header and bitmap info header */
	READ_STATE_PALETTE,	/* Reading the palette */
	READ_STATE_BITMASKS,	/* Reading the bitmasks for BI_BITFIELDS */
	READ_STATE_DATA,	/* Reading the actual image data */
	READ_STATE_ERROR,	/* An error occurred; further data will be ignored */
	READ_STATE_DONE		/* Done reading the image; further data will be ignored */
} ReadState;
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/*

DumpBIH printf's the values in a BitmapInfoHeader to the screen, for
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debugging purposes.

*/
#if DUMPBIH
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static void DumpBIH(unsigned char *BIH)
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{
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	printf("biSize      = %i \n",
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	       (int) (BIH[3] << 24) + (BIH[2] << 16) + (BIH[1] << 8) +
	       (BIH[0]));
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	printf("biWidth     = %i \n",
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	       (int) (BIH[7] << 24) + (BIH[6] << 16) + (BIH[5] << 8) +
	       (BIH[4]));
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	printf("biHeight    = %i \n",
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	       (int) (BIH[11] << 24) + (BIH[10] << 16) + (BIH[9] << 8) +
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	       (BIH[8]));
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	printf("biPlanes    = %i \n", (int) (BIH[13] << 8) + (BIH[12]));
	printf("biBitCount  = %i \n", (int) (BIH[15] << 8) + (BIH[14]));
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	printf("biCompress  = %i \n",
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	       (int) (BIH[19] << 24) + (BIH[18] << 16) + (BIH[17] << 8) +
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	       (BIH[16]));
	printf("biSizeImage = %i \n",
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	       (int) (BIH[23] << 24) + (BIH[22] << 16) + (BIH[21] << 8) +
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	       (BIH[20]));
	printf("biXPels     = %i \n",
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	       (int) (BIH[27] << 24) + (BIH[26] << 16) + (BIH[25] << 8) +
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	       (BIH[24]));
	printf("biYPels     = %i \n",
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	       (int) (BIH[31] << 24) + (BIH[30] << 16) + (BIH[29] << 8) +
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	       (BIH[28]));
	printf("biClrUsed   = %i \n",
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	       (int) (BIH[35] << 24) + (BIH[34] << 16) + (BIH[33] << 8) +
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	       (BIH[32]));
	printf("biClrImprtnt= %i \n",
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	       (int) (BIH[39] << 24) + (BIH[38] << 16) + (BIH[37] << 8) +
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	       (BIH[36]));
}
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#endif
/* struct headerpair contains the decoded width/height/depth info for
   the current bitmap */
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struct headerpair {
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	guint32 size;
	gint32 width;
	gint32 height;
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	guint depth;
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	guint Negative;		/* Negative = 1 -> top down BMP,
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				   Negative = 0 -> bottom up BMP */
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	guint  n_colors;
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};
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/* Data needed for the "state" during decompression */
struct bmp_compression_state {
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	gint phase;
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	gint run;
	gint count;
	gint x, y;
	guchar *p;
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};
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/* Progressive loading */

struct bmp_progressive_state {
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	GdkPixbufModuleSizeFunc size_func;
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	GdkPixbufModulePreparedFunc prepared_func;
	GdkPixbufModuleUpdatedFunc updated_func;
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	gpointer user_data;

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	ReadState read_state;

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	guint LineWidth;
	guint Lines;		/* # of finished lines */
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	guchar *buff;
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	guint BufferSize;
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	guint BufferPadding;
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	guint BufferDone;
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	guchar (*Colormap)[3];
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	gint Type;		/*
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				   32 = RGB + alpha
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				   24 = RGB
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				   16 = RGB
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				   4  = 4 bpp colormapped
				   8  = 8 bpp colormapped
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				   1  = 1 bit bitonal
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				 */
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	guint Compressed;
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	struct bmp_compression_state compr;
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	struct headerpair Header;	/* Decoded (BE->CPU) header */

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	/* Bit masks, shift amounts, and significant bits for BI_BITFIELDS coding */
	int r_mask, r_shift, r_bits;
	int g_mask, g_shift, g_bits;
	int b_mask, b_shift, b_bits;
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	int a_mask, a_shift, a_bits;
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	GdkPixbuf *pixbuf;	/* Our "target" */
};

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static gpointer
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gdk_pixbuf__bmp_image_begin_load(GdkPixbufModuleSizeFunc size_func,
                                 GdkPixbufModulePreparedFunc prepared_func,
				 GdkPixbufModuleUpdatedFunc updated_func,
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                                 gpointer user_data,
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                                 GError **error);
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static gboolean gdk_pixbuf__bmp_image_stop_load(gpointer data, GError **error);
static gboolean gdk_pixbuf__bmp_image_load_increment(gpointer data,
                                                     const guchar * buf,
                                                     guint size,
                                                     GError **error);
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/* Picks up a 32-bit little-endian integer starting at the specified location.
 * Does it by hand instead of dereferencing a simple (gint *) cast due to
 * alignment constraints many platforms.
 */
static int
lsb_32 (guchar *src)
{
	return src[0] | (src[1] << 8) | (src[2] << 16) | (src[3] << 24);
}

/* Same as above, but for 16-bit little-endian integers. */
static short
lsb_16 (guchar *src)
{
	return src[0] | (src[1] << 8);
}

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static gboolean grow_buffer (struct bmp_progressive_state *State,
                             GError **error)
{
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  guchar *tmp;

  if (State->BufferSize == 0) {
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    g_set_error_literal (error,
                         GDK_PIXBUF_ERROR,
                         GDK_PIXBUF_ERROR_CORRUPT_IMAGE,
                         _("BMP image has bogus header data"));
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    State->read_state = READ_STATE_ERROR;
    return FALSE;
  }

  tmp = g_try_realloc (State->buff, State->BufferSize);

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  if (!tmp) {
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    g_set_error_literal (error,
                         GDK_PIXBUF_ERROR,
                         GDK_PIXBUF_ERROR_INSUFFICIENT_MEMORY,
                         _("Not enough memory to load bitmap image"));
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    State->read_state = READ_STATE_ERROR;
    return FALSE;
  }
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  State->buff = tmp;
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  return TRUE;
}

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static gboolean
decode_bitmasks (guchar *buf,
		 struct bmp_progressive_state *State, 
		 GError **error);

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static gboolean DecodeHeader(unsigned char *BFH, unsigned char *BIH,
                             struct bmp_progressive_state *State,
                             GError **error)
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{
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	gint clrUsed;

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	/* First check for the two first bytes content. A sane
	   BMP file must start with bytes 0x42 0x4D.  */
	if (*BFH != 0x42 || *(BFH + 1) != 0x4D) {
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		g_set_error_literal (error,
                                     GDK_PIXBUF_ERROR,
                                     GDK_PIXBUF_ERROR_CORRUPT_IMAGE,
                                     _("BMP image has bogus header data"));
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		State->read_state = READ_STATE_ERROR;
		return FALSE;
	}

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        /* FIXME this is totally unrobust against bogus image data. */
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	if (State->BufferSize < lsb_32 (&BIH[0]) + 14) {
		State->BufferSize = lsb_32 (&BIH[0]) + 14;
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		if (!grow_buffer (State, error))
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			return FALSE;
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		return TRUE;
	}

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#if DUMPBIH
	DumpBIH(BIH);
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#endif    
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	State->Header.size = lsb_32 (&BIH[0]);
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	if (State->Header.size == 124) {
                /* BMP v5 */
		State->Header.width = lsb_32 (&BIH[4]);
		State->Header.height = lsb_32 (&BIH[8]);
		State->Header.depth = lsb_16 (&BIH[14]);
		State->Compressed = lsb_32 (&BIH[16]);
	} else if (State->Header.size == 108) {
                /* BMP v4 */
		State->Header.width = lsb_32 (&BIH[4]);
		State->Header.height = lsb_32 (&BIH[8]);
		State->Header.depth = lsb_16 (&BIH[14]);
		State->Compressed = lsb_32 (&BIH[16]);
	} else if (State->Header.size == 64) {
                /* BMP OS/2 v2 */
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		State->Header.width = lsb_32 (&BIH[4]);
		State->Header.height = lsb_32 (&BIH[8]);
		State->Header.depth = lsb_16 (&BIH[14]);
		State->Compressed = lsb_32 (&BIH[16]);
	} else if (State->Header.size == 40) {
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                /* BMP v3 */ 
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		State->Header.width = lsb_32 (&BIH[4]);
		State->Header.height = lsb_32 (&BIH[8]);
		State->Header.depth = lsb_16 (&BIH[14]);
		State->Compressed = lsb_32 (&BIH[16]);
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	} else if (State->Header.size == 12) {
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                /* BMP OS/2 */
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		State->Header.width = lsb_16 (&BIH[4]);
		State->Header.height = lsb_16 (&BIH[6]);
		State->Header.depth = lsb_16 (&BIH[10]);
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		State->Compressed = BI_RGB;
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	} else {
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		g_set_error_literal (error,
                                     GDK_PIXBUF_ERROR,
                                     GDK_PIXBUF_ERROR_CORRUPT_IMAGE,
                                     _("BMP image has unsupported header size"));
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		State->read_state = READ_STATE_ERROR;
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		return FALSE;
	}
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	if (State->Header.size == 12)
		clrUsed = 1 << State->Header.depth;
	else
		clrUsed = (int) (BIH[35] << 24) + (BIH[34] << 16) + (BIH[33] << 8) + (BIH[32]);

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	if (clrUsed != 0)
		State->Header.n_colors = clrUsed;
	else
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            State->Header.n_colors = (1 << State->Header.depth);
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	if (State->Header.n_colors > (1 << State->Header.depth)) {
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		g_set_error_literal (error,
                                     GDK_PIXBUF_ERROR,
                                     GDK_PIXBUF_ERROR_CORRUPT_IMAGE,
                                     _("BMP image has bogus header data"));
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		State->read_state = READ_STATE_ERROR;
		return FALSE;
	}

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	State->Type = State->Header.depth;	/* This may be less trivial someday */
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	/* Negative heights indicates bottom-down pixelorder */
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	if (State->Header.height < 0) {
		State->Header.height = -State->Header.height;
		State->Header.Negative = 1;
	}
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	if (State->Header.Negative && 
	    (State->Compressed != BI_RGB && State->Compressed != BI_BITFIELDS))
	{
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		g_set_error_literal (error,
                                     GDK_PIXBUF_ERROR,
                                     GDK_PIXBUF_ERROR_CORRUPT_IMAGE,
                                     _("Topdown BMP images cannot be compressed"));
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		State->read_state = READ_STATE_ERROR;
		return FALSE;
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	}
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	if (State->Header.width <= 0 || State->Header.height == 0 ||
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	    (State->Compressed == BI_RLE4 && State->Type != 4)    ||
	    (State->Compressed == BI_RLE8 && State->Type != 8)	  ||
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	    (State->Compressed == BI_BITFIELDS && !(State->Type == 16 || State->Type == 32)) ||
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	    (State->Compressed > BI_BITFIELDS)) {
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		g_set_error_literal (error,
                                     GDK_PIXBUF_ERROR,
                                     GDK_PIXBUF_ERROR_CORRUPT_IMAGE,
                                     _("BMP image has bogus header data"));
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		State->read_state = READ_STATE_ERROR;
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		return FALSE;
	}

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	if (State->Type == 32)
		State->LineWidth = State->Header.width * 4;
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	else if (State->Type == 24)
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		State->LineWidth = State->Header.width * 3;
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	else if (State->Type == 16)
		State->LineWidth = State->Header.width * 2;
	else if (State->Type == 8)
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		State->LineWidth = State->Header.width * 1;
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	else if (State->Type == 4)
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		State->LineWidth = (State->Header.width + 1) / 2;
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	else if (State->Type == 1) {
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		State->LineWidth = State->Header.width / 8;
		if ((State->Header.width & 7) != 0)
			State->LineWidth++;
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	} else {
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		g_set_error_literal (error,
                                     GDK_PIXBUF_ERROR,
                                     GDK_PIXBUF_ERROR_CORRUPT_IMAGE,
                                     _("BMP image has bogus header data"));
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		State->read_state = READ_STATE_ERROR;
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		return FALSE;
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	}
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	/* Pad to a 32 bit boundary */
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	if (((State->LineWidth % 4) > 0)
	    && (State->Compressed == BI_RGB || State->Compressed == BI_BITFIELDS))
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		State->LineWidth = (State->LineWidth / 4) * 4 + 4;

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	if (State->pixbuf == NULL) {
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		if (State->size_func) {
			gint width = State->Header.width;
			gint height = State->Header.height;

			(*State->size_func) (&width, &height, State->user_data);
			if (width == 0 || height == 0) {
				State->read_state = READ_STATE_DONE;
				State->BufferSize = 0;
				return TRUE;
			}
		}

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		if (State->Type == 32 || 
		    State->Compressed == BI_RLE4 || 
		    State->Compressed == BI_RLE8)
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			State->pixbuf =
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				gdk_pixbuf_new(GDK_COLORSPACE_RGB, TRUE, 8,
					       (gint) State->Header.width,
					       (gint) State->Header.height);
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		else
			State->pixbuf =
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				gdk_pixbuf_new(GDK_COLORSPACE_RGB, FALSE, 8,
					       (gint) State->Header.width,
					       (gint) State->Header.height);
		
		if (State->pixbuf == NULL) {
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			g_set_error_literal (error,
                                             GDK_PIXBUF_ERROR,
                                             GDK_PIXBUF_ERROR_INSUFFICIENT_MEMORY,
                                             _("Not enough memory to load bitmap image"));
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			State->read_state = READ_STATE_ERROR;
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			return FALSE;
			}
		
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		if (State->prepared_func != NULL)
			/* Notify the client that we are ready to go */
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			(*State->prepared_func) (State->pixbuf, NULL, State->user_data);
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		/* make all pixels initially transparent */
		if (State->Compressed == BI_RLE4 || State->Compressed == BI_RLE8) {
			memset (State->pixbuf->pixels, 0, State->pixbuf->rowstride * State->Header.height);
			State->compr.p = State->pixbuf->pixels 
				+ State->pixbuf->rowstride * (State->Header.height- 1);
		}
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	}
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	State->BufferDone = 0;
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	if (State->Type <= 8) {
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                gint samples;

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		State->read_state = READ_STATE_PALETTE;
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		/* Allocate enough to hold the palette */
	        samples = (State->Header.size == 12 ? 3 : 4);
		State->BufferSize = State->Header.n_colors * samples;

		/* Skip over everything between the palette and the data.
		   This protects us against a malicious BFH[10] value.
                */
		State->BufferPadding = (lsb_32 (&BFH[10]) - 14 - State->Header.size) - State->BufferSize;

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	} else if (State->Compressed == BI_RGB) {
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		if (State->BufferSize < lsb_32 (&BFH[10]))
		{
			/* skip over padding between headers and image data */
			State->read_state = READ_STATE_HEADERS;
			State->BufferDone = State->BufferSize;
			State->BufferSize = lsb_32 (&BFH[10]);
		}
		else
		{
			State->read_state = READ_STATE_DATA;
			State->BufferSize = State->LineWidth;
		}
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	} else if (State->Compressed == BI_BITFIELDS) {
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               if (State->Header.size == 108 || State->Header.size == 124) 
               {
			/* v4 and v5 have the bitmasks in the header */
			if (!decode_bitmasks (&BIH[40], State, error)) {
			       State->read_state = READ_STATE_ERROR;
			       return FALSE;
                        }
               }
               else 
               {
		       State->read_state = READ_STATE_BITMASKS;
		       State->BufferSize = 12;
               }
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	} else {
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		g_set_error_literal (error,
                                     GDK_PIXBUF_ERROR,
                                     GDK_PIXBUF_ERROR_CORRUPT_IMAGE,
                                     _("BMP image has bogus header data"));
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		State->read_state = READ_STATE_ERROR;
		return FALSE;
	}
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	if (!grow_buffer (State, error)) 
		return FALSE;
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        return TRUE;
}

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static gboolean DecodeColormap (guchar *buff,
				struct bmp_progressive_state *State,
				GError **error)
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{
	gint i;
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	gint samples;
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	g_assert (State->read_state == READ_STATE_PALETTE);

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	samples = (State->Header.size == 12 ? 3 : 4);
	if (State->BufferSize < State->Header.n_colors * samples) {
		State->BufferSize = State->Header.n_colors * samples;
		if (!grow_buffer (State, error))
			return FALSE;
		return TRUE;
	}

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	State->Colormap = g_malloc0 ((1 << State->Header.depth) * sizeof (*State->Colormap));
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	for (i = 0; i < State->Header.n_colors; i++)
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	{
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		State->Colormap[i][0] = buff[i * samples];
		State->Colormap[i][1] = buff[i * samples + 1];
		State->Colormap[i][2] = buff[i * samples + 2];
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#ifdef DUMPCMAP
		g_print ("color %d %x %x %x\n", i,
			 State->Colormap[i][0],
			 State->Colormap[i][1],
			 State->Colormap[i][2]);
#endif
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	}

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	State->read_state = READ_STATE_DATA;

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	State->BufferDone = 0;
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	if (!(State->Compressed == BI_RGB || State->Compressed == BI_BITFIELDS))
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		State->BufferSize = 2;
	else
		State->BufferSize = State->LineWidth;
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	if (!grow_buffer (State, error))
		return FALSE;
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	return TRUE;
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}

/* Finds the lowest set bit and the number of set bits */
static void
find_bits (int n, int *lowest, int *n_set)
{
	int i;

	*n_set = 0;

	for (i = 31; i >= 0; i--)
		if (n & (1 << i)) {
			*lowest = i;
			(*n_set)++;
		}
}

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/* Decodes the bitmasks for BI_BITFIELDS coding */
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static gboolean
decode_bitmasks (guchar *buf,
		 struct bmp_progressive_state *State, 
		 GError **error)
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{
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        State->a_mask = State->a_shift = State->a_bits = 0;
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	State->r_mask = buf[0] | (buf[1] << 8) | (buf[2] << 16) | (buf[3] << 24);
	buf += 4;

	State->g_mask = buf[0] | (buf[1] << 8) | (buf[2] << 16) | (buf[3] << 24);
	buf += 4;

	State->b_mask = buf[0] | (buf[1] << 8) | (buf[2] << 16) | (buf[3] << 24);

	find_bits (State->r_mask, &State->r_shift, &State->r_bits);
	find_bits (State->g_mask, &State->g_shift, &State->g_bits);
	find_bits (State->b_mask, &State->b_shift, &State->b_bits);

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        /* v4 and v5 have an alpha mask */
        if (State->Header.size == 108 || State->Header.size == 124) {
	      buf += 4;
	      State->a_mask = buf[0] | (buf[1] << 8) | (buf[2] << 16) | (buf[3] << 24);
	      find_bits (State->a_mask, &State->a_shift, &State->a_bits);
        }

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	if (State->r_bits == 0 || State->g_bits == 0 || State->b_bits == 0) {
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                if (State->Type == 16) {
		       State->r_mask = 0x7c00;
		       State->r_shift = 10;
		       State->g_mask = 0x03e0;
		       State->g_shift = 5;
		       State->b_mask = 0x001f;
		       State->b_shift = 0;

		       State->r_bits = State->g_bits = State->b_bits = 5;
                }
                else {
		       State->r_mask = 0x00ff0000;
		       State->r_shift = 16;
		       State->g_mask = 0x0000ff00;
		       State->g_shift = 8;
		       State->b_mask = 0x000000ff;
		       State->b_shift = 0;
		       State->a_mask = 0xff000000;
		       State->a_shift = 24;

		       State->r_bits = State->g_bits = State->b_bits = State->a_bits = 8;
                }
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	}

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        if (State->r_bits > 8) {
          State->r_shift += State->r_bits - 8;
          State->r_bits = 8;
        }
        if (State->g_bits > 8) {
          State->g_shift += State->g_bits - 8;
          State->g_bits = 8;
        }
        if (State->b_bits > 8) {
          State->b_shift += State->b_bits - 8;
          State->b_bits = 8;
        }
        if (State->a_bits > 8) {
          State->a_shift += State->a_bits - 8;
          State->a_bits = 8;
        }

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	State->read_state = READ_STATE_DATA;
	State->BufferDone = 0;
	State->BufferSize = State->LineWidth;
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	if (!grow_buffer (State, error)) 
		return FALSE;

	return TRUE;
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}

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/*
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 * func - called when we have pixmap created (but no image data)
 * user_data - passed as arg 1 to func
 * return context (opaque to user)
 */

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static gpointer
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gdk_pixbuf__bmp_image_begin_load(GdkPixbufModuleSizeFunc size_func,
                                 GdkPixbufModulePreparedFunc prepared_func,
				 GdkPixbufModuleUpdatedFunc updated_func,
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                                 gpointer user_data,
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                                 GError **error)
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{
	struct bmp_progressive_state *context;
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	context = g_new0(struct bmp_progressive_state, 1);
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	context->size_func = size_func;
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	context->prepared_func = prepared_func;
	context->updated_func = updated_func;
	context->user_data = user_data;

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	context->read_state = READ_STATE_HEADERS;

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	context->BufferSize = 26;
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	context->BufferPadding = 0;
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	context->buff = g_malloc(26);
	context->BufferDone = 0;
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	/* 14 for the BitmapFileHeader, 12 for the BitmapImageHeader */
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	context->Colormap = NULL;
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	context->Lines = 0;

	context->Type = 0;

	memset(&context->Header, 0, sizeof(struct headerpair));
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	memset(&context->compr, 0, sizeof(struct bmp_compression_state));
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	context->pixbuf = NULL;
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	return (gpointer) context;
}

/*
 * context - returned from image_begin_load
 *
 * free context, unref gdk_pixbuf
 */
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static gboolean gdk_pixbuf__bmp_image_stop_load(gpointer data, GError **error)
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{
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	gboolean retval = TRUE;
	
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	struct bmp_progressive_state *context =
	    (struct bmp_progressive_state *) data;

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        /* FIXME this thing needs to report errors if
         * we have unused image data
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         */
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	g_return_val_if_fail(context != NULL, TRUE);
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	g_free(context->Colormap);
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	if (context->pixbuf)
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		g_object_unref(context->pixbuf);
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	if (context->read_state == READ_STATE_HEADERS) {
                if (error && *error == NULL) {
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                        g_set_error_literal (error,
                                             GDK_PIXBUF_ERROR,
                                             GDK_PIXBUF_ERROR_CORRUPT_IMAGE,
                                             _("Premature end-of-file encountered"));
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                }
		retval = FALSE;
	}
	
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	g_free(context->buff);
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	g_free(context);
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        return retval;
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}


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/*
The OneLineXX functions are called when 1 line worth of data is present.
OneLine24 is the 24 bpp-version.
*/
static void OneLine32(struct bmp_progressive_state *context)
{
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	int i;
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	guchar *pixels;
	guchar *src;
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	if (!context->Header.Negative)
		pixels = (context->pixbuf->pixels +
			  context->pixbuf->rowstride * (context->Header.height - context->Lines - 1));
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	else
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		pixels = (context->pixbuf->pixels +
			  context->pixbuf->rowstride * context->Lines);

	src = context->buff;

	if (context->Compressed == BI_BITFIELDS) {
		int r_lshift, r_rshift;
		int g_lshift, g_rshift;
		int b_lshift, b_rshift;
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		int a_lshift, a_rshift;
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		r_lshift = 8 - context->r_bits;
		g_lshift = 8 - context->g_bits;
		b_lshift = 8 - context->b_bits;
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		a_lshift = 8 - context->a_bits;
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		r_rshift = context->r_bits - r_lshift;
		g_rshift = context->g_bits - g_lshift;
		b_rshift = context->b_bits - b_lshift;
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		a_rshift = context->a_bits - a_lshift;
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		for (i = 0; i < context->Header.width; i++) {
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			int v, r, g, b, a;
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			v = src[0] | (src[1] << 8) | (src[2] << 16) | (src[3] << 24);
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			r = (v & context->r_mask) >> context->r_shift;
			g = (v & context->g_mask) >> context->g_shift;
			b = (v & context->b_mask) >> context->b_shift;
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			a = (v & context->a_mask) >> context->a_shift;
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			*pixels++ = (r << r_lshift) | (r >> r_rshift);
			*pixels++ = (g << g_lshift) | (g >> g_rshift);
			*pixels++ = (b << b_lshift) | (b >> b_rshift);
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                        if (context->a_bits)
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			  *pixels++ = 0xff - ((a << a_lshift) | (a >> a_rshift));
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                        else
                          *pixels++ = 0xff;
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			src += 4;
		}
	} else
		for (i = 0; i < context->Header.width; i++) {
			*pixels++ = src[2];
			*pixels++ = src[1];
			*pixels++ = src[0];
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			*pixels++ = 0xff;
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			src += 4;
		}
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}

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static void OneLine24(struct bmp_progressive_state *context)
{
	gint X;
	guchar *Pixels;

	X = 0;
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	if (context->Header.Negative == 0)
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		Pixels = (context->pixbuf->pixels +
			  context->pixbuf->rowstride *
			  (context->Header.height - context->Lines - 1));
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	else
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		Pixels = (context->pixbuf->pixels +
			  context->pixbuf->rowstride *
			  context->Lines);
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	while (X < context->Header.width) {
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		Pixels[X * 3 + 0] = context->buff[X * 3 + 2];
		Pixels[X * 3 + 1] = context->buff[X * 3 + 1];
		Pixels[X * 3 + 2] = context->buff[X * 3 + 0];
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		X++;
	}

}

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static void OneLine16(struct bmp_progressive_state *context)
{
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	int i;
	guchar *pixels;
	guchar *src;
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	if (!context->Header.Negative)
		pixels = (context->pixbuf->pixels +
			  context->pixbuf->rowstride * (context->Header.height - context->Lines - 1));
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	else
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		pixels = (context->pixbuf->pixels +
			  context->pixbuf->rowstride * context->Lines);

	src = context->buff;

	if (context->Compressed == BI_BITFIELDS) {
		int r_lshift, r_rshift;
		int g_lshift, g_rshift;
		int b_lshift, b_rshift;

		r_lshift = 8 - context->r_bits;
		g_lshift = 8 - context->g_bits;
		b_lshift = 8 - context->b_bits;

		r_rshift = context->r_bits - r_lshift;
		g_rshift = context->g_bits - g_lshift;
		b_rshift = context->b_bits - b_lshift;

		for (i = 0; i < context->Header.width; i++) {
			int v, r, g, b;

			v = (int) src[0] | ((int) src[1] << 8);

			r = (v & context->r_mask) >> context->r_shift;
			g = (v & context->g_mask) >> context->g_shift;
			b = (v & context->b_mask) >> context->b_shift;

			*pixels++ = (r << r_lshift) | (r >> r_rshift);
			*pixels++ = (g << g_lshift) | (g >> g_rshift);
			*pixels++ = (b << b_lshift) | (b >> b_rshift);

			src += 2;
		}
	} else
		for (i = 0; i < context->Header.width; i++) {
			int v, r, g, b;

			v = src[0] | (src[1] << 8);

			r = (v >> 10) & 0x1f;
			g = (v >> 5) & 0x1f;
			b = v & 0x1f;

			*pixels++ = (r << 3) | (r >> 2);
			*pixels++ = (g << 3) | (g >> 2);
			*pixels++ = (b << 3) | (b >> 2);
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			src += 2;
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		}
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}

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static void OneLine8(struct bmp_progressive_state *context)
{
	gint X;
	guchar *Pixels;

	X = 0;
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	if (context->Header.Negative == 0)
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		Pixels = (context->pixbuf->pixels +
			  context->pixbuf->rowstride *
			  (context->Header.height - context->Lines - 1));
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	else
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		Pixels = (context->pixbuf->pixels +
			  context->pixbuf->rowstride *
			  context->Lines);
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	while (X < context->Header.width) {
		Pixels[X * 3 + 0] =
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		    context->Colormap[context->buff[X]][2];
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		Pixels[X * 3 + 1] =
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		    context->Colormap[context->buff[X]][1];
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		Pixels[X * 3 + 2] =
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		    context->Colormap[context->buff[X]][0];
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		X++;
	}
}

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