Redid io-png for gdk-pixbuf. Note that it'll add an opaque alpha channel

Redid io-png for gdk-pixbuf.  Note that it'll add an opaque alpha channel
to any png that doesn't have one, and will convert greyscale PNGs to RGBA.

gdk-pixbuf/io-png.c

 /*
- * io-png.c: GdkPixBuf image loader for PNG files.
+ * io-png.c: GdkPixBuf I/O for PNG files.
  *
  * Author:
- *    Miguel de Icaza (miguel@gnu.org)
+ *    Mark Crichton <crichton@gimp.org>
  *
  */
 #include <config.h>
 #include <stdio.h>
+#include <glib.h>
 #include "gdk-pixbuf.h"
 #include "gdk-pixbuf-io.h"
 #include <png.h>
 
 /* Shared library entry point */
-GdkPixBuf *
-image_load (FILE *f);
+GdkPixBuf *image_load(FILE * f)
 {
-	png_structp png;
-	png_infop   info_ptr, end_info;
-	int width, height, depth, color_type, interlace_type;
-	int have_alpha, number_passes;
-	art_u8 *data;
-	
-	g_return_val_if_fail (filename != NULL, NULL);
+	png_structp png_ptr;
+	png_infop info_ptr, end_info;
+	gint i, depth, ctype, inttype, passes;
+	png_uint_32 w, h, x, y;
+	png_bytepp rows;
+	art_u8 *pixels, *temp, *rowdata;
+	GdkPixBuf *pixbuf;
 
-	png = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
-	if (png)
-		return NULL;
+	g_return_val_if_fail (f != NULL, NULL);
 
-	info_ptr = png_create_info_struct (png);
-	if (!info_ptr){
-		png_destroy_read_struct (&png, NULL, NULL);
+	png_ptr = png_create_read_struct (PNG_LIBPNG_VER_STRING, NULL, NULL,
+		  NULL);
+
+	info_ptr = png_create_info_struct (png_ptr);
+	if (!info_ptr) {
+		png_destroy_read_struct(&png_ptr, NULL, NULL);
 		return NULL;
 	}
 
-	end_info = png_create_info_struct (png);
-	if (!end_info){
-		png_destroy_read_struct (&png, &info_ptr, NULL);
-		return NULL:
+	end_info = png_create_info_struct (png_ptr);
+	if (!end_info) {
+		png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
+		return NULL;
 	}
 
-	if (setjmp (png->jmpbuf)){
-		png_destroy_read_struct (&png, &info_ptr, &end_info);
+	if (setjmp(png_ptr->jmpbuf)) {
+		png_destroy_read_struct(&png_ptr, &info_ptr, &end_info);
 		return NULL;
 	}
 
-	png_init_io (pngptr, f);
+	png_init_io(png_ptr, f);
+	png_read_info(png_ptr, info_ptr);
 
-	png_read_info (png, info_ptr);
-	png_get_IHDR (png, info_ptr, &width, &height, &depth, &color_type, &interlace_type, NULL, NULL);
+	png_get_IHDR(png_ptr, info_ptr, &w, &h, &depth, &ctype, &inttype,
+		     NULL, NULL);
 
-	if (color_type == color_type == PNG_COLOR_TYPE_PALETTE)
-		png_set_expand (png);
-
-	/*
-	 * Strip 16 bit information to 8 bit
+	/* Ok, we want to work with 24 bit images.
+	 * However, PNG can vary depth per channel.
+	 * So, we use the png_set_expand function to expand
+	 * everything into a format libart expects.
+	 * We also use png_set_strip_16 to reduce down to 8 bit/chan.
 	 */
-	png_set_strip_16 (png);
 
-	/*
-	 * Extract multiple pixels with bit depths 1, 2 and 4 from a single
-	 * byte into separate bytes
-	 */
-	png_set_packing (png);
+	if (ctype == PNG_COLOR_TYPE_PALETTE && depth <= 8)
+		png_set_expand(png_ptr);
 
-	/*
-	 * Makes the PNG file to be rendered into RGB or RGBA
-	 * modes (no matter of the bit depth nor the image
-	 * mode
-	 */
-	png_set_expand (png);
+	if (ctype == PNG_COLOR_TYPE_GRAY && depth < 8)
+		png_set_expand(png_ptr);
 
-	/*
-	 * Simplify loading by always having 4 bytes
-	 */
-	png_set_filler (png, 0xff, PNG_FILLER_AFTER);
+	if (png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS))
+		png_set_expand(png_ptr);
 
-	if (color_type & PNG_COLOR_MASK_ALPHA)
-		have_alpha = 1
-	else
-		have_alpha = 0;
-	
-	data = art_alloc (width * height * (3 + have_alpha));
-	if (!data){
-		png_destroy_read_struct (&png, &info_ptr, &end_info);
+	if (depth == 16)
+		png_set_strip_16(png_ptr);
+
+	/* We also have png "packing" bits into bytes if < 8 */
+	if (depth < 8)
+		png_set_packing(png_ptr);
+
+	/* Add filler bits to non-alpha PNGs */
+	/* make it 255, full opaque */
+	if (depth == 8 && ctype == PNG_COLOR_TYPE_RGB)
+		png_set_filler(png_ptr, 0xFF, PNG_FILLER_AFTER);
+
+	/* Lastly, if the PNG is greyscale, convert to RGB */
+	if (ctype == PNG_COLOR_TYPE_GRAY || ctype == PNG_COLOR_TYPE_GRAY_ALPHA)
+		png_set_gray_to_rgb(png_ptr);
+
+	/* ...and if we're interlaced... */
+	passes = png_set_interlace_handling(png_ptr);
+
+	/* Update our info structs */
+	png_read_update_info(png_ptr, info_ptr);
+
+	/* Allocate some memory and set up row array */
+	/* This "inhales vigirously"... */
+	pixels = g_malloc(w*h*4);
+	rows = g_malloc(h*sizeof(png_bytep));
+
+	if ((!pixels) || (!rows)) {
+		png_destroy_read_struct(&png_ptr, &info_ptr, &end_info);
 		return NULL;
 	}
 
-	number_passes = png_set_interlace_handling (png);
+	/* Icky code, but it has to be done... */
+	for (i = 0; i < h; i++) {
+		if ((rows[i] = g_malloc(w*sizeof(art_u8)*4)) == NULL) {
+			int n;
+			for (n = 0; n < i; n++)
+				g_free(rows[i]);
+			g_free(rows);
+			png_destroy_read_struct(&png_ptr, &info_ptr, &end_info);
+			return NULL;
+		}
+	}
+	
+	/* And we FINALLY get here... */
+	png_read_image(png_ptr, rows);
+	png_destroy_read_struct(&png_ptr, &info_ptr, &end_info);
+	
+	/* Now stuff the bytes into pixels & free rows[y] */
+	/* RGBA order */
+	temp = pixels;
+	for (y = 0; y < h; y++) {
+		(png_bytep)rowdata = rows[y];
+		for (x = 0; x < w; x++) {
+			temp[0] = rowdata[(x*4)];
+			temp[1] = rowdata[(x*4)+1];
+			temp[2] = rowdata[(x*4)+2];
+			temp[3] = rowdata[(x*4)+3];
+			temp += 4;
+		}
+		g_free(rows[y]);
+	}
+	g_free(rows);
+
+	/* Return the GdkPixBuf */
+	pixbuf = g_new(GdkPixBuf, 1);
+
+	pixbuf->art_pixbuf = art_pixbuf_new_rgba (pixels, w, h, (w*4));
+
+	/* Ok, I'm anal...shoot me */
+	if (!(pixbuf->art_pixbuf))
+		return NULL;
+	pixbuf->ref_count = 0;
+	pixbuf->unref_func = NULL;
+
+	return pixbuf;
 }