various optimizations

1 files changed, 16 insertions, 7 deletions

diff --git a/src/jpeg.c b/src/jpeg.c
index 6d3b40c..dde41ce 100644
--- a/src/jpeg.c
+++ b/src/jpeg.c
@@ -15,6 +15,7 @@ unsigned char *loadjpeg(char *filename, int *width, int *height){
 	JSAMPARRAY buffer;
 	int row_stride;
 	int i = 0;
+	int j;
 	int x, y;
 	unsigned char *retbuf;
 
@@ -27,23 +28,31 @@ unsigned char *loadjpeg(char *filename, int *width, int *height){
 	jpeg_create_decompress(&cinfo);
 	jpeg_stdio_src(&cinfo, infile);
 	jpeg_read_header(&cinfo, TRUE);
+	cinfo.do_fancy_upsampling = 0;
+	cinfo.do_block_smoothing = 0;
+	cinfo.quantize_colors = 0;
+	cinfo.dct_method = JDCT_IFAST;
 	jpeg_start_decompress(&cinfo);
 	*width = cinfo.output_width;
 	*height = cinfo.output_height;
-	retbuf = malloc(cinfo.output_components * (cinfo.output_width * cinfo.output_height));
+	retbuf = malloc(4 * cinfo.output_components * (cinfo.output_width * cinfo.output_height));
 
 	if(cinfo.output_components != 3){
 		fprintf(stderr, "TODO: greyscale images are not supported\n");
 		exit(1);
 	}
 	row_stride = cinfo.output_width * cinfo.output_components;
-	buffer = (*cinfo.mem->alloc_sarray)((j_common_ptr) &cinfo, JPOOL_IMAGE, row_stride, 1);
-	for(y = 0; y < cinfo.output_height; y++){
-		jpeg_read_scanlines(&cinfo, buffer, 1);
-		for(x = 0; x < row_stride; x++){
-			retbuf[i++] = buffer[0][x];
+	buffer = (*cinfo.mem->alloc_sarray)((j_common_ptr)&cinfo, JPOOL_IMAGE, row_stride, 16);
+	for(y = 0; y < cinfo.output_height; ){
+		int n = jpeg_read_scanlines(&cinfo, buffer, 16);
+		for(j = 0; j < n; j++){
+			for(x = 0; x < row_stride;){
+				retbuf[i++] = buffer[j][x++];
+				retbuf[i++] = buffer[j][x++];
+				retbuf[i++] = buffer[j][x++];
+			}
 		}
-		assert(i % *width == 0);
+		y += n;
 	}
 	jpeg_finish_decompress(&cinfo);
 	jpeg_destroy_decompress(&cinfo);