Add support for parsing GIF images.

4 files changed, 597 insertions, 4 deletions

diff --git a/source/cbz/mucbz.c b/source/cbz/mucbz.c
index 14be8333..91f6e9db 100644
--- a/source/cbz/mucbz.c
+++ b/source/cbz/mucbz.c
@@ -6,8 +6,8 @@ typedef struct cbz_document_s cbz_document;
 typedef struct cbz_page_s cbz_page;
 
 static const char *cbz_ext_list[] = {
-	".jpg", ".jpeg", ".png",
-	".JPG", ".JPEG", ".PNG",
+	".jpg", ".jpeg", ".png", ".gif",
+	".JPG", ".JPEG", ".PNG", ".GIF",
 	NULL
 };
 
diff --git a/source/cbz/muimg.c b/source/cbz/muimg.c
index ac6997ee..0a01e2b0 100644
--- a/source/cbz/muimg.c
+++ b/source/cbz/muimg.c
@@ -158,13 +158,15 @@ img_recognize(fz_context *doc, const char *magic)
 	{
 		if (!fz_strcasecmp(ext, ".png") || !fz_strcasecmp(ext, ".jpg") ||
 			!fz_strcasecmp(ext, ".jpeg") || !fz_strcasecmp(ext, ".jfif") ||
-			!fz_strcasecmp(ext, ".jfif-tbnl") || !fz_strcasecmp(ext, ".jpe"))
+			!fz_strcasecmp(ext, ".jfif-tbnl") || !fz_strcasecmp(ext, ".jpe") ||
+			!fz_strcasecmp(ext, ".gif"))
 			return 100;
 	}
 	if (!strcmp(magic, "png") || !strcmp(magic, "image/png") ||
 		!strcmp(magic, "jpg") || !strcmp(magic, "image/jpeg") ||
 		!strcmp(magic, "jpeg") || !strcmp(magic, "image/pjpeg") ||
-		!strcmp(magic, "jpe") || !strcmp(magic, "jfif"))
+		!strcmp(magic, "jpe") || !strcmp(magic, "jfif") ||
+		!strcmp(magic, "gif") || !strcmp(magic, "image/gif"))
 		return 100;
 
 	return 0;
diff --git a/source/fitz/image.c b/source/fitz/image.c
index a63aaf9a..9a4d35a6 100644
--- a/source/fitz/image.c
+++ b/source/fitz/image.c
@@ -245,6 +245,9 @@ standard_image_get_pixmap(fz_context *ctx, fz_image *image, int w, int h, int *l
 	case FZ_IMAGE_PNG:
 		tile = fz_load_png(ctx, image->buffer->buffer->data, image->buffer->buffer->len);
 		break;
+	case FZ_IMAGE_GIF:
+		tile = fz_load_gif(ctx, image->buffer->buffer->data, image->buffer->buffer->len);
+		break;
 	case FZ_IMAGE_TIFF:
 		tile = fz_load_tiff(ctx, image->buffer->buffer->data, image->buffer->buffer->len);
 		break;
@@ -533,6 +536,11 @@ fz_new_image_from_buffer(fz_context *ctx, fz_buffer *buffer)
 			bc->params.type = FZ_IMAGE_TIFF;
 			fz_load_tiff_info(ctx, buf, len, &w, &h, &xres, &yres, &cspace);
 		}
+		else if (memcmp(buf, "GIF", 3) == 0)
+		{
+			bc->params.type = FZ_IMAGE_GIF;
+			fz_load_gif_info(ctx, buf, len, &w, &h, &xres, &yres, &cspace);
+		}
 		else
 			fz_throw(ctx, FZ_ERROR_GENERIC, "unknown image file format");
 	}
diff --git a/source/fitz/load-gif.c b/source/fitz/load-gif.c
new file mode 100644
index 00000000..71d120b0
--- /dev/null
+++ b/source/fitz/load-gif.c
@@ -0,0 +1,583 @@
+#include "mupdf/fitz.h"
+
+struct info
+{
+	int gif89a;
+	unsigned int width, height;
+	unsigned char aspect;
+	unsigned int xres, yres;
+
+	unsigned int image_left, image_top;
+	unsigned int image_width, image_height;
+	unsigned int image_interlaced;
+
+	int has_gct;
+	unsigned int gct_entries;
+	unsigned char *gct;
+	unsigned int gct_background;
+
+	int has_lct;
+	unsigned int lct_entries;
+	unsigned char *lct;
+
+	int has_transparency;
+	unsigned int transparent;
+	unsigned char *mask;
+
+	unsigned char *samples;
+};
+
+/* default color table, where the first two entries are black and white */
+static const unsigned char dct[256 * 3] = {
+	0x00, 0x00, 0x00, 0xff, 0xff, 0xff, 0x01, 0x01, 0x01, 0x02, 0x02, 0x02,
+	0x03, 0x03, 0x03, 0x04, 0x04, 0x04, 0x05, 0x05, 0x05, 0x06, 0x06, 0x06,
+	0x07, 0x07, 0x07, 0x08, 0x08, 0x08, 0x09, 0x09, 0x09, 0x0a, 0x0a, 0x0a,
+	0x0b, 0x0b, 0x0b, 0x0c, 0x0c, 0x0c, 0x0d, 0x0d, 0x0d, 0x0e, 0x0e, 0x0e,
+	0x0f, 0x0f, 0x0f, 0x10, 0x10, 0x10, 0x11, 0x11, 0x11, 0x12, 0x12, 0x12,
+	0x13, 0x13, 0x13, 0x14, 0x14, 0x14, 0x15, 0x15, 0x15, 0x16, 0x16, 0x16,
+	0x17, 0x17, 0x17, 0x18, 0x18, 0x18, 0x19, 0x19, 0x19, 0x1a, 0x1a, 0x1a,
+	0x1b, 0x1b, 0x1b, 0x1c, 0x1c, 0x1c, 0x1d, 0x1d, 0x1d, 0x1e, 0x1e, 0x1e,
+	0x1f, 0x1f, 0x1f, 0x20, 0x20, 0x20, 0x21, 0x21, 0x21, 0x22, 0x22, 0x22,
+	0x23, 0x23, 0x23, 0x24, 0x24, 0x24, 0x25, 0x25, 0x25, 0x26, 0x26, 0x26,
+	0x27, 0x27, 0x27, 0x28, 0x28, 0x28, 0x29, 0x29, 0x29, 0x2a, 0x2a, 0x2a,
+	0x2b, 0x2b, 0x2b, 0x2c, 0x2c, 0x2c, 0x2d, 0x2d, 0x2d, 0x2e, 0x2e, 0x2e,
+	0x2f, 0x2f, 0x2f, 0x30, 0x30, 0x30, 0x31, 0x31, 0x31, 0x32, 0x32, 0x32,
+	0x33, 0x33, 0x33, 0x34, 0x34, 0x34, 0x35, 0x35, 0x35, 0x36, 0x36, 0x36,
+	0x37, 0x37, 0x37, 0x38, 0x38, 0x38, 0x39, 0x39, 0x39, 0x3a, 0x3a, 0x3a,
+	0x3b, 0x3b, 0x3b, 0x3c, 0x3c, 0x3c, 0x3d, 0x3d, 0x3d, 0x3e, 0x3e, 0x3e,
+	0x3f, 0x3f, 0x3f, 0x40, 0x40, 0x40, 0x41, 0x41, 0x41, 0x42, 0x42, 0x42,
+	0x43, 0x43, 0x43, 0x44, 0x44, 0x44, 0x45, 0x45, 0x45, 0x46, 0x46, 0x46,
+	0x47, 0x47, 0x47, 0x48, 0x48, 0x48, 0x49, 0x49, 0x49, 0x4a, 0x4a, 0x4a,
+	0x4b, 0x4b, 0x4b, 0x4c, 0x4c, 0x4c, 0x4d, 0x4d, 0x4d, 0x4e, 0x4e, 0x4e,
+	0x4f, 0x4f, 0x4f, 0x50, 0x50, 0x50, 0x51, 0x51, 0x51, 0x52, 0x52, 0x52,
+	0x53, 0x53, 0x53, 0x54, 0x54, 0x54, 0x55, 0x55, 0x55, 0x56, 0x56, 0x56,
+	0x57, 0x57, 0x57, 0x58, 0x58, 0x58, 0x59, 0x59, 0x59, 0x5a, 0x5a, 0x5a,
+	0x5b, 0x5b, 0x5b, 0x5c, 0x5c, 0x5c, 0x5d, 0x5d, 0x5d, 0x5e, 0x5e, 0x5e,
+	0x5f, 0x5f, 0x5f, 0x60, 0x60, 0x60, 0x61, 0x61, 0x61, 0x62, 0x62, 0x62,
+	0x63, 0x63, 0x63, 0x64, 0x64, 0x64, 0x65, 0x65, 0x65, 0x66, 0x66, 0x66,
+	0x67, 0x67, 0x67, 0x68, 0x68, 0x68, 0x69, 0x69, 0x69, 0x6a, 0x6a, 0x6a,
+	0x6b, 0x6b, 0x6b, 0x6c, 0x6c, 0x6c, 0x6d, 0x6d, 0x6d, 0x6e, 0x6e, 0x6e,
+	0x6f, 0x6f, 0x6f, 0x70, 0x70, 0x70, 0x71, 0x71, 0x71, 0x72, 0x72, 0x72,
+	0x73, 0x73, 0x73, 0x74, 0x74, 0x74, 0x75, 0x75, 0x75, 0x76, 0x76, 0x76,
+	0x77, 0x77, 0x77, 0x78, 0x78, 0x78, 0x79, 0x79, 0x79, 0x7a, 0x7a, 0x7a,
+	0x7b, 0x7b, 0x7b, 0x7c, 0x7c, 0x7c, 0x7d, 0x7d, 0x7d, 0x7e, 0x7e, 0x7e,
+	0x7f, 0x7f, 0x7f, 0x80, 0x80, 0x80, 0x81, 0x81, 0x81, 0x82, 0x82, 0x82,
+	0x83, 0x83, 0x83, 0x84, 0x84, 0x84, 0x85, 0x85, 0x85, 0x86, 0x86, 0x86,
+	0x87, 0x87, 0x87, 0x88, 0x88, 0x88, 0x89, 0x89, 0x89, 0x8a, 0x8a, 0x8a,
+	0x8b, 0x8b, 0x8b, 0x8c, 0x8c, 0x8c, 0x8d, 0x8d, 0x8d, 0x8e, 0x8e, 0x8e,
+	0x8f, 0x8f, 0x8f, 0x90, 0x90, 0x90, 0x91, 0x91, 0x91, 0x92, 0x92, 0x92,
+	0x93, 0x93, 0x93, 0x94, 0x94, 0x94, 0x95, 0x95, 0x95, 0x96, 0x96, 0x96,
+	0x97, 0x97, 0x97, 0x98, 0x98, 0x98, 0x99, 0x99, 0x99, 0x9a, 0x9a, 0x9a,
+	0x9b, 0x9b, 0x9b, 0x9c, 0x9c, 0x9c, 0x9d, 0x9d, 0x9d, 0x9e, 0x9e, 0x9e,
+	0x9f, 0x9f, 0x9f, 0xa0, 0xa0, 0xa0, 0xa1, 0xa1, 0xa1, 0xa2, 0xa2, 0xa2,
+	0xa3, 0xa3, 0xa3, 0xa4, 0xa4, 0xa4, 0xa5, 0xa5, 0xa5, 0xa6, 0xa6, 0xa6,
+	0xa7, 0xa7, 0xa7, 0xa8, 0xa8, 0xa8, 0xa9, 0xa9, 0xa9, 0xaa, 0xaa, 0xaa,
+	0xab, 0xab, 0xab, 0xac, 0xac, 0xac, 0xad, 0xad, 0xad, 0xae, 0xae, 0xae,
+	0xaf, 0xaf, 0xaf, 0xb0, 0xb0, 0xb0, 0xb1, 0xb1, 0xb1, 0xb2, 0xb2, 0xb2,
+	0xb3, 0xb3, 0xb3, 0xb4, 0xb4, 0xb4, 0xb5, 0xb5, 0xb5, 0xb6, 0xb6, 0xb6,
+	0xb7, 0xb7, 0xb7, 0xb8, 0xb8, 0xb8, 0xb9, 0xb9, 0xb9, 0xba, 0xba, 0xba,
+	0xbb, 0xbb, 0xbb, 0xbc, 0xbc, 0xbc, 0xbd, 0xbd, 0xbd, 0xbe, 0xbe, 0xbe,
+	0xbf, 0xbf, 0xbf, 0xc0, 0xc0, 0xc0, 0xc1, 0xc1, 0xc1, 0xc2, 0xc2, 0xc2,
+	0xc3, 0xc3, 0xc3, 0xc4, 0xc4, 0xc4, 0xc5, 0xc5, 0xc5, 0xc6, 0xc6, 0xc6,
+	0xc7, 0xc7, 0xc7, 0xc8, 0xc8, 0xc8, 0xc9, 0xc9, 0xc9, 0xca, 0xca, 0xca,
+	0xcb, 0xcb, 0xcb, 0xcc, 0xcc, 0xcc, 0xcd, 0xcd, 0xcd, 0xce, 0xce, 0xce,
+	0xcf, 0xcf, 0xcf, 0xd0, 0xd0, 0xd0, 0xd1, 0xd1, 0xd1, 0xd2, 0xd2, 0xd2,
+	0xd3, 0xd3, 0xd3, 0xd4, 0xd4, 0xd4, 0xd5, 0xd5, 0xd5, 0xd6, 0xd6, 0xd6,
+	0xd7, 0xd7, 0xd7, 0xd8, 0xd8, 0xd8, 0xd9, 0xd9, 0xd9, 0xda, 0xda, 0xda,
+	0xdb, 0xdb, 0xdb, 0xdc, 0xdc, 0xdc, 0xdd, 0xdd, 0xdd, 0xde, 0xde, 0xde,
+	0xdf, 0xdf, 0xdf, 0xe0, 0xe0, 0xe0, 0xe1, 0xe1, 0xe1, 0xe2, 0xe2, 0xe2,
+	0xe3, 0xe3, 0xe3, 0xe4, 0xe4, 0xe4, 0xe5, 0xe5, 0xe5, 0xe6, 0xe6, 0xe6,
+	0xe7, 0xe7, 0xe7, 0xe8, 0xe8, 0xe8, 0xe9, 0xe9, 0xe9, 0xea, 0xea, 0xea,
+	0xeb, 0xeb, 0xeb, 0xec, 0xec, 0xec, 0xed, 0xed, 0xed, 0xee, 0xee, 0xee,
+	0xef, 0xef, 0xef, 0xf0, 0xf0, 0xf0, 0xf1, 0xf1, 0xf1, 0xf2, 0xf2, 0xf2,
+	0xf3, 0xf3, 0xf3, 0xf4, 0xf4, 0xf4, 0xf5, 0xf5, 0xf5, 0xf6, 0xf6, 0xf6,
+	0xf7, 0xf7, 0xf7, 0xf8, 0xf8, 0xf8, 0xf9, 0xf9, 0xf9, 0xfa, 0xfa, 0xfa,
+	0xfb, 0xfb, 0xfb, 0xfc, 0xfc, 0xfc, 0xfd, 0xfd, 0xfd, 0xfe, 0xfe, 0xfe,
+};
+
+static unsigned char *
+gif_read_subblocks(fz_context *ctx, struct info *info, unsigned char *p, unsigned char *end, fz_buffer *buf)
+{
+	int len;
+
+	do
+	{
+		if (end - p < 1)
+			fz_throw(ctx, FZ_ERROR_GENERIC, "premature end in data subblocks in gif image");
+		len = *p;
+		p += 1;
+
+		if (len > 0)
+		{
+			if (end - p < len)
+				fz_throw(ctx, FZ_ERROR_GENERIC, "premature end in data subblock in gif image");
+			if (buf)
+				fz_write_buffer(ctx, buf, p, len);
+			p += len;
+		}
+	} while (len > 0);
+
+	return p;
+}
+
+static unsigned char *
+gif_read_header(fz_context *ctx, struct info *info, unsigned char *p, unsigned char *end)
+{
+	if (end - p < 6)
+		fz_throw(ctx, FZ_ERROR_GENERIC, "premature end in header in gif image");
+
+	if (memcmp(&p[0], "GIF", 3))
+		fz_throw(ctx, FZ_ERROR_GENERIC, "invalid signature in gif image");
+	if (memcmp(&p[3], "87a", 3) && memcmp(&p[3], "89a", 3))
+		fz_throw(ctx, FZ_ERROR_GENERIC, "unsupported version in gif image");
+
+	info->gif89a = !memcmp(p, "GIF89a", 6);
+
+	return p + 6;
+}
+
+static unsigned char *
+gif_read_lsd(fz_context *ctx, struct info *info, unsigned char *p, unsigned char *end)
+{
+	if (end - p < 7)
+		fz_throw(ctx, FZ_ERROR_GENERIC, "premature end in logical screen descriptor in gif image");
+
+	info->width = p[1] << 8 | p[0];
+	info->height = p[3] << 8 | p[2];
+	info->has_gct = (p[4] >> 7) & 0x1;
+	if (info->has_gct)
+	{
+		info->gct_entries = 1 << ((p[4] & 0x7) + 1);
+		info->gct_background = p[5];
+	}
+	info->aspect = p[6];
+
+	info->xres = 96;
+	info->yres= 96;
+	if (info->aspect > 0)
+		info->yres = (((float) info->aspect + 15) / 64) * 96;
+
+	return p + 7;
+}
+
+static unsigned char *
+gif_read_gct(fz_context *ctx, struct info *info, unsigned char *p, unsigned char *end)
+{
+	if (end - p < info->gct_entries * 3)
+		fz_throw(ctx, FZ_ERROR_GENERIC, "premature end in global color table in gif image");
+
+	info->gct = fz_malloc(ctx, info->gct_entries * 3);
+	memmove(info->gct, p, info->gct_entries * 3);
+
+	return p + info->gct_entries * 3;
+}
+
+static unsigned char *
+gif_read_id(fz_context *ctx, struct info *info, unsigned char *p, unsigned char *end)
+{
+	if (end - p < 10)
+		fz_throw(ctx, FZ_ERROR_GENERIC, "premature end in image descriptor in gif image");
+
+	info->image_left = p[2] << 8 | p[1];
+	info->image_top = p[4] << 8 | p[3];
+	info->image_width = p[6] << 8 | p[5];
+	info->image_height = p[8] << 8 | p[7];
+	info->has_lct = (p[9] >> 7) & 0x1;
+	info->image_interlaced = (p[9] >> 6) & 0x1;
+
+	if (info->has_lct)
+		info->lct_entries = 1 << ((p[9] & 0x7) + 1);
+
+	return p + 10;
+}
+
+static unsigned char *
+gif_read_lct(fz_context *ctx, struct info *info, unsigned char *p, unsigned char *end)
+{
+	if (end - p < info->lct_entries * 3)
+		fz_throw(ctx, FZ_ERROR_GENERIC, "premature end in local color table in gif image");
+
+	info->lct = fz_malloc(ctx, info->lct_entries * 3);
+	memmove(info->lct, p, info->lct_entries * 3);
+
+	return p + info->lct_entries * 3;
+}
+
+static void
+gif_read_line(fz_context *ctx, struct info *info, const unsigned char *ct, unsigned int y, unsigned char *sp)
+{
+	unsigned int index = (info->image_top + y) * info->width + info->image_left;
+	unsigned char *dp = &info->samples[index * 3];
+	unsigned char *mp = &info->mask[index];
+	int x, k;
+
+	for (x = 0; x < info->image_width; x++, sp++, mp++, dp += 3)
+		if (!info->has_transparency || *sp != info->transparent)
+		{
+			*mp = 0x02;
+			for (k = 0; k < 3; k++)
+				dp[k] = ct[*sp * 3 + k];
+		}
+		else if (*mp == 0x01)
+			*mp = 0x00;
+}
+
+static unsigned char *
+gif_read_tbid(fz_context *ctx, struct info *info, unsigned char *p, unsigned char *end)
+{
+	fz_stream *stm, *lzwstm = NULL;
+	unsigned int mincodesize, y;
+	fz_buffer *compressed = NULL, *uncompressed = NULL;
+	const unsigned char *ct;
+	unsigned char *sp;
+
+	if (end - p < 1)
+		fz_throw(ctx, FZ_ERROR_GENERIC, "premature end in table based image data in gif image");
+
+	mincodesize = *p;
+
+	fz_var(compressed);
+	fz_var(lzwstm);
+	fz_var(uncompressed);
+
+	fz_try(ctx)
+	{
+		compressed = fz_new_buffer(ctx, 0);
+		p = gif_read_subblocks(ctx, info, p + 1, end, compressed);
+
+		stm = fz_open_buffer(ctx, compressed);
+		lzwstm = fz_open_lzwd(ctx, stm, 0, mincodesize + 1, 1);
+
+		uncompressed = fz_read_all(ctx, lzwstm, info->width * info->height);
+		sp = uncompressed->data;
+
+		if (info->has_lct)
+			ct = info->lct;
+		else if (info->has_gct)
+			ct = info->gct;
+		else
+			ct = dct;
+
+		if (info->image_interlaced)
+		{
+			for (y = 0; y < info->image_height; y += 8, sp += info->image_width)
+				gif_read_line(ctx, info, ct, y, sp);
+			for (y = 4; y < info->image_height; y += 8, sp += info->image_width)
+				gif_read_line(ctx, info, ct, y, sp);
+			for (y = 2; y < info->image_height; y += 4, sp += info->image_width)
+				gif_read_line(ctx, info, ct, y, sp);
+			for (y = 1; y < info->image_height; y += 2, sp += info->image_width)
+				gif_read_line(ctx, info, ct, y, sp);
+		}
+		else
+			for (y = 0; y < info->image_height; y++, sp += info->image_width)
+				gif_read_line(ctx, info, ct, y, sp);
+	}
+	fz_always(ctx)
+	{
+		fz_drop_buffer(ctx, uncompressed);
+		fz_drop_buffer(ctx, compressed);
+		fz_drop_stream(ctx, lzwstm);
+	}
+	fz_catch(ctx)
+	{
+		fz_rethrow_message(ctx, "cannot read compressed table based image data in gif image");
+	}
+
+	return p;
+}
+
+static unsigned char *
+gif_read_gce(fz_context *ctx, struct info *info, unsigned char *p, unsigned char *end)
+{
+	if (end - p < 8)
+		fz_throw(ctx, FZ_ERROR_GENERIC, "premature end in graphic control extension in gif image");
+	if (p[2] != 0x04)
+		fz_throw(ctx, FZ_ERROR_GENERIC, "out of range graphic control extension block size in gif image");
+
+	info->has_transparency = p[3] & 0x1;
+	if (info->has_transparency)
+		info->transparent = p[6];
+
+	return p + 8;
+}
+
+static unsigned char *
+gif_read_ce(fz_context *ctx, struct info *info, unsigned char *p, unsigned char *end)
+{
+	fz_try(ctx)
+	{
+		p = gif_read_subblocks(ctx, info, p + 2, end, NULL);
+	}
+	fz_catch(ctx)
+	{
+		fz_rethrow_message(ctx, "cannot read comment extension text in gif image");
+	}
+
+	return p;
+}
+
+static unsigned char*
+gif_read_pte(fz_context *ctx, struct info *info, unsigned char *p, unsigned char *end)
+{
+	if (end - p < 15)
+		fz_throw(ctx, FZ_ERROR_GENERIC, "premature end in plain text extension in gif image");
+	if (p[2] != 0x0c)
+		fz_throw(ctx, FZ_ERROR_GENERIC, "out of range plain text extension block size in gif image");
+
+	fz_try(ctx)
+	{
+		p = gif_read_subblocks(ctx, info, p + 15, end, NULL);
+	}
+	fz_catch(ctx)
+	{
+		fz_rethrow_message(ctx, "cannot read plain text extension text in gif image");
+	}
+
+	return p;
+}
+
+/*
+NETSCAPE2.0
+	http://odur.let.rug.nl/~kleiweg/gif/netscape.html
+	http://www.vurdalakov.net/misc/gif/netscape-looping-application-extension
+	http://www.vurdalakov.net/misc/gif/netscape-buffering-application-extension
+	https://code.google.com/p/gifdotnet/source/browse/src/GifDotNet/GifApplicationExtensionBlock.cs#95
+	http://trac.webkit.org/browser/trunk/Source/WebCore/platform/image-decoders/gif/GIFImageReader.cpp#L617
+
+ANIMEXTS1.0
+	http://www.vurdalakov.net/misc/gif/animexts-looping-application-extension
+	https://code.google.com/p/gifdotnet/source/browse/src/GifDotNet/GifApplicationExtensionBlock.cs#95
+
+ICCRGBG1012
+	http://www.color.org/icc1V42.pdf
+
+XMP DataXMP
+	http://wwwimages.adobe.com/www.adobe.com/content/dam/Adobe/en/devnet/xmp/pdfs/XMPSpecificationPart3.pdf
+
+fractint
+	http://fractint.net/fractsvn/trunk/fractint/common/loadfile.c
+
+ZGATEXTI5 ZGATILEI5 ZGACTRLI5 ZGANPIMGI5
+ZGAVECTI5 ZGAALPHAI5 ZGATITLE4.0 ZGATEXTI4.0
+	Zoner GIF animator 4.0 and 5.0
+*/
+static unsigned char *
+gif_read_ae(fz_context *ctx, struct info *info, unsigned char *p, unsigned char *end)
+{
+	static char *ignorable[] = {
+		"NETSACPE2.0", "ANIMEXTS1.0", "ICCRGBG1012", "XMP DataXMP",
+		"ZGATEXTI5\0\0", "ZGATILEI5\0\0", "ZGANPIMGI5\0", "ZGACTRLI5\0\0",
+		"ZGAVECTI5\0\0", "ZGAALPHAI5\0", "ZGATITLE4.0", "ZGATEXTI4.0",
+	};
+	int i, ignored;
+
+	if (end - p < 14)
+		fz_throw(ctx, FZ_ERROR_GENERIC, "premature end in application extension in gif image");
+	if (p[2] != 0x0b)
+		fz_throw(ctx, FZ_ERROR_GENERIC, "out of range application extension block size in gif image");
+
+	ignored = 0;
+	for (i = 0; i < nelem(ignorable); i++)
+		ignored |= memcmp(&p[3], ignorable[i], 8 + 3);
+	if (!ignored)
+	{
+		char extension[9];
+		memmove(extension, &p[3], 8);
+		extension[8] = '\0';
+		fz_warn(ctx, "ignoring unsupported application extension '%s' in gif image", extension);
+	}
+
+	fz_try(ctx)
+	{
+		p = gif_read_subblocks(ctx, info, p + 14, end, NULL);
+	}
+	fz_catch(ctx)
+	{
+		fz_rethrow_message(ctx, "cannot read application extension data in gif image");
+	}
+
+	return p;
+}
+
+static void
+gif_read_image(fz_context *ctx, struct info *info, unsigned char *p, int total, int only_metadata)
+{
+	unsigned char *end = p + total;
+
+	memset(info, 0x00, sizeof (*info));
+
+	/* Read header */
+	p = gif_read_header(ctx, info, p, end);
+
+	/* Read logical screen descriptor */
+	p = gif_read_lsd(ctx, info, p, end);
+
+	if (only_metadata)
+		return;
+
+	info->samples = fz_malloc(ctx, info->width * info->height * 3);
+	info->mask = fz_calloc(ctx, info->width * info->height, 1);
+
+	/* Read optional global color table */
+	if (info->has_gct)
+	{
+		unsigned char *bp, *dp = info->samples;
+		unsigned int x, y, k;
+
+		p = gif_read_gct(ctx, info, p, end);
+		bp = &info->gct[info->gct_background * 3];
+
+		memset(info->mask, 0x01, info->width * info->height);
+
+		for (y = 0; y < info->height; y++)
+			for (x = 0; x < info->width; x++, dp += 3)
+				for (k = 0; k < 3; k++)
+					dp[k] = bp[k];
+	}
+
+	fz_var(info->lct);
+
+	fz_try(ctx)
+	{
+		while (1)
+		{
+			/* Read block indicator */
+			if (end - p < 1)
+				fz_throw(ctx, FZ_ERROR_GENERIC, "premature end of block indicator in gif image");
+
+			/* Read trailer */
+			if (p[0] == 0x3b)
+			{
+				break;
+			}
+			/* Read extension */
+			else if (p[0] == 0x21)
+			{
+				/* Read extension label */
+				if (end - p < 2)
+					fz_throw(ctx, FZ_ERROR_GENERIC, "premature end in extension label in gif image");
+
+				if (p[1] == 0x01 && info->gif89a)
+				{
+					/* Read plain text extension */
+					p = gif_read_pte(ctx, info, p, end);
+
+					/* Graphic control extension applies only to the graphic rendering block following it */
+					info->transparent = 0;
+					info->has_transparency = 0;
+				}
+				else if (p[1] == 0xf9 && info->gif89a)
+					/* Read graphic control extension */
+					p = gif_read_gce(ctx, info, p, end);
+				else if (p[1] == 0xfe && info->gif89a)
+					/* Read comment extension */
+					p = gif_read_ce(ctx, info, p, end);
+				else if (p[1] == 0xff && info->gif89a)
+					/* Read application extension */
+					p = gif_read_ae(ctx, info, p, end);
+				else
+					fz_throw(ctx, FZ_ERROR_GENERIC, "unsupported extension label %02x in gif image", p[1]);
+			}
+			/* Read image descriptor */
+			else if (p[0] == 0x2c)
+			{
+				p = gif_read_id(ctx, info, p, end);
+
+				if (info->has_lct)
+					/* Read local color table */
+					p = gif_read_lct(ctx, info, p, end);
+
+				/* Read table based image data */
+				p = gif_read_tbid(ctx, info, p, end);
+
+				/* Graphic control extension applies only to the graphic rendering block following it */
+				info->transparent = 0;
+				info->has_transparency = 0;
+
+				/* Image descriptor applies only to the table based image data following it */
+				info->image_left = info->image_top = 0;
+				info->image_width = info->width;
+				info->image_height = info->height;
+				info->image_interlaced = 0;
+				fz_free(ctx, info->lct);
+				info->lct = NULL;
+				info->has_lct = 0;
+			}
+			else
+				fz_throw(ctx, FZ_ERROR_GENERIC, "unsupported block indicator %02x in gif image", p[0]);
+		}
+	}
+	fz_always(ctx)
+	{
+		fz_free(ctx, info->lct);
+		fz_free(ctx, info->gct);
+	}
+	fz_catch(ctx)
+	{
+		fz_free(ctx, info->mask);
+		fz_free(ctx, info->samples);
+		fz_rethrow(ctx);
+	}
+}
+
+static void
+gif_mask_transparency(fz_context *ctx, fz_pixmap *image, struct info *info)
+{
+	unsigned char *mp = info->mask;
+	unsigned char *dp = image->samples;
+	int x, y;
+
+	for (y = 0; y < info->height; y++)
+		for (x = 0; x < info->width; x++, mp++, dp += image->n)
+			if (*mp == 0x00)
+				dp[image->n - 1] = 0;
+}
+
+fz_pixmap *
+fz_load_gif(fz_context *ctx, unsigned char *p, int total)
+{
+	fz_pixmap *image;
+	struct info gif;
+
+	gif_read_image(ctx, &gif, p, total, 0);
+
+	fz_try(ctx)
+	{
+		image = fz_new_pixmap(ctx, fz_device_rgb(ctx), gif.width, gif.height);
+	}
+	fz_catch(ctx)
+	{
+		fz_rethrow_message(ctx, "out of memory loading gif image");
+	}
+
+	image->xres = gif.xres;
+	image->yres = gif.yres;
+
+	fz_unpack_tile(ctx, image, gif.samples, 3, 8, gif.width * 3, 0);
+
+	if (gif.mask)
+	{
+		gif_mask_transparency(ctx, image, &gif);
+		fz_premultiply_pixmap(ctx, image);
+	}
+
+	fz_free(ctx, gif.samples);
+	fz_free(ctx, gif.mask);
+
+	return image;
+}
+
+void
+fz_load_gif_info(fz_context *ctx, unsigned char *p, int total, int *wp, int *hp, int *xresp, int *yresp, fz_colorspace **cspacep)
+{
+	struct info gif;
+
+	gif_read_image(ctx, &gif, p, total, 1);
+
+	*cspacep = fz_device_rgb(ctx);
+	*wp = gif.width;
+	*hp = gif.height;
+	*xresp = gif.xres;
+	*yresp = gif.yres;
+}