bmp: Add support for embedded JPEG images.

Reintroduce fz_load_jpeg() (previously removed in 12c1466) improved with:
 * application agnostic memory handler support from 6a8abce
 * colorspace context from 93bd1ff
 * resolution detection from 4dc6cbe

2 files changed, 128 insertions, 3 deletions

diff --git a/source/fitz/load-bmp.c b/source/fitz/load-bmp.c
index e3ba67f5..cb314587 100644
--- a/source/fitz/load-bmp.c
+++ b/source/fitz/load-bmp.c
@@ -67,6 +67,7 @@ enum {
 	BI_RLE8 = 1,
 	BI_RLE4 = 2,
 	BI_BITFIELDS = 3,
+	BI_JPEG = 4,
 };
 
 struct info
@@ -725,7 +726,8 @@ bmp_read_image(fz_context *ctx, struct info *info, unsigned char *p, int total,
 		fz_throw(ctx, FZ_ERROR_GENERIC, "dimensions (%d x %d) out of range in bmp image",
 				info->width, info->height);
 	if (info->compression != BI_RGB && info->compression != BI_RLE8 &&
-			info->compression != BI_RLE4 && info->compression != BI_BITFIELDS)
+			info->compression != BI_RLE4 && info->compression != BI_BITFIELDS &&
+			info->compression != BI_JPEG)
 		fz_throw(ctx, FZ_ERROR_GENERIC, "unsupported compression method (%d) in bmp image", info->compression);
 	if ((info->compression == BI_RGB && info->bitcount != 1 &&
 			info->bitcount != 2 && info->bitcount != 4 &&
@@ -733,7 +735,8 @@ bmp_read_image(fz_context *ctx, struct info *info, unsigned char *p, int total,
 			info->bitcount != 24 && info->bitcount != 32) ||
 			(info->compression == BI_RLE8 && info->bitcount != 8) ||
 			(info->compression == BI_RLE4 && info->bitcount != 4) ||
-			(info->compression == BI_BITFIELDS && info->bitcount != 16 && info->bitcount != 32))
+			(info->compression == BI_BITFIELDS && info->bitcount != 16 && info->bitcount != 32) ||
+			(info->compression == BI_JPEG && info->bitcount != 0))
 		fz_throw(ctx, FZ_ERROR_GENERIC, "invalid bits per pixel (%d) for compression (%d) in bmp image",
 				info->bitcount, info->compression);
 	if (info->rbits > 0 && info->rbits != 4 && info->rbits != 5 && info->rbits != 8)
@@ -743,7 +746,16 @@ bmp_read_image(fz_context *ctx, struct info *info, unsigned char *p, int total,
 	if (info->bbits > 0 && info->bbits != 4 && info->bbits != 5 && info->bbits != 8)
 		fz_throw(ctx, FZ_ERROR_GENERIC, "unsupported %d bit blue mask in bmp image", info->bbits);
 
-	if (!only_metadata)
+	if (only_metadata)
+		return NULL;
+
+	if (info->compression == BI_JPEG)
+	{
+		if (p - begin < info->offset)
+			p = begin + info->offset;
+		return fz_load_jpeg(ctx, p, end - p);
+	}
+	else
 	{
 		p = bmp_read_color_table(ctx, info, p, begin + info->offset);
 		if (p - begin < info->offset)
diff --git a/source/fitz/load-jpeg.c b/source/fitz/load-jpeg.c
index 2640a8a4..29db9bcf 100644
--- a/source/fitz/load-jpeg.c
+++ b/source/fitz/load-jpeg.c
@@ -214,6 +214,119 @@ static int extract_app13_resolution(jpeg_saved_marker_ptr marker, int *xres, int
 	return 0;
 }
 
+fz_pixmap *
+fz_load_jpeg(fz_context *ctx, unsigned char *rbuf, int rlen)
+{
+	struct jpeg_decompress_struct cinfo;
+	struct jpeg_error_mgr err;
+	struct jpeg_source_mgr src;
+	unsigned char *row[1], *sp, *dp;
+	fz_colorspace *colorspace;
+	unsigned int x;
+	int k;
+	fz_pixmap *image = NULL;
+
+	fz_var(image);
+	fz_var(row);
+
+	row[0] = NULL;
+
+	fz_try(ctx)
+	{
+		cinfo.client_data = ctx;
+		cinfo.err = jpeg_std_error(&err);
+		err.error_exit = error_exit;
+
+		fz_jpg_mem_init(ctx, &cinfo);
+
+		jpeg_create_decompress(&cinfo);
+
+		cinfo.src = &src;
+		src.init_source = init_source;
+		src.fill_input_buffer = fill_input_buffer;
+		src.skip_input_data = skip_input_data;
+		src.resync_to_restart = jpeg_resync_to_restart;
+		src.term_source = term_source;
+		src.next_input_byte = rbuf;
+		src.bytes_in_buffer = rlen;
+
+		jpeg_save_markers(&cinfo, JPEG_APP0+1, 0xffff);
+		jpeg_save_markers(&cinfo, JPEG_APP0+13, 0xffff);
+
+		jpeg_read_header(&cinfo, 1);
+
+		jpeg_start_decompress(&cinfo);
+
+		if (cinfo.output_components == 1)
+			colorspace = fz_device_gray(ctx);
+		else if (cinfo.output_components == 3)
+			colorspace = fz_device_rgb(ctx);
+		else if (cinfo.output_components == 4)
+			colorspace = fz_device_cmyk(ctx);
+		else
+			fz_throw(ctx, FZ_ERROR_GENERIC, "bad number of components in jpeg: %d", cinfo.num_components);
+
+		image = fz_new_pixmap(ctx, colorspace, cinfo.output_width, cinfo.output_height);
+
+		if (extract_exif_resolution(cinfo.marker_list, &image->xres, &image->yres))
+			/* XPS prefers EXIF resolution to JFIF density */;
+		else if (extract_app13_resolution(cinfo.marker_list, &image->xres, &image->yres))
+			/* XPS prefers APP13 resolution to JFIF density */;
+		else if (cinfo.density_unit == 1)
+		{
+			image->xres = cinfo.X_density;
+			image->yres = cinfo.Y_density;
+		}
+		else if (cinfo.density_unit == 2)
+		{
+			image->xres = cinfo.X_density * 254 / 100;
+			image->yres = cinfo.Y_density * 254 / 100;
+		}
+
+		if (image->xres <= 0) image->xres = 96;
+		if (image->yres <= 0) image->yres = 96;
+
+		fz_clear_pixmap(ctx, image);
+
+		row[0] = fz_malloc(ctx, cinfo.output_components * cinfo.output_width);
+		dp = image->samples;
+		while (cinfo.output_scanline < cinfo.output_height)
+		{
+			jpeg_read_scanlines(&cinfo, row, 1);
+			sp = row[0];
+			for (x = 0; x < cinfo.output_width; x++)
+			{
+				for (k = 0; k < cinfo.output_components; k++)
+					*dp++ = *sp++;
+				*dp++ = 255;
+			}
+		}
+	}
+	fz_always(ctx)
+	{
+		fz_free(ctx, row[0]);
+		row[0] = NULL;
+		fz_try(ctx)
+		{
+			/* Annoyingly, jpeg_finish_decompress can throw */
+			jpeg_finish_decompress(&cinfo);
+		}
+		fz_catch(ctx)
+		{
+			/* Ignore any errors here */
+		}
+		jpeg_destroy_decompress(&cinfo);
+		fz_jpg_mem_term(&cinfo);
+	}
+	fz_catch(ctx)
+	{
+		fz_drop_pixmap(ctx, image);
+		fz_rethrow(ctx);
+	}
+
+	return image;
+}
+
 void
 fz_load_jpeg_info(fz_context *ctx, unsigned char *rbuf, int rlen, int *xp, int *yp, int *xresp, int *yresp, fz_colorspace **cspacep)
 {