Hi guys,
I've written and tested a small patch that increases efficiency
(particularly in small-cache systems) of loading JPEG images: override
the recommended lines with what we've already allocated; increase
batch size from 4 to 8 lines.
Please consider for inclusion and tweak as needed (eg reducing the
batch size to the original limit of 4).
Many thanks,
Daniel
Signed-off-by: Daniel J Blueman <daniel.blue...@gmail.com>
--
Daniel J Blueman
diff --git a/gdk-pixbuf/io-jpeg.c b/gdk-pixbuf/io-jpeg.c
index 680a209..77a37e6 100644
--- a/gdk-pixbuf/io-jpeg.c
+++ b/gdk-pixbuf/io-jpeg.c
@@ -46,6 +46,7 @@
/* we are a "source manager" as far as libjpeg is concerned */
#define JPEG_PROG_BUF_SIZE 65536
+#define LINEBUF_SIZE 8
typedef struct {
struct jpeg_source_mgr pub; /* public fields */
@@ -454,7 +455,7 @@ gdk_pixbuf__jpeg_image_load (FILE *f, GError **error)
char otag_str[5];
GdkPixbuf * volatile pixbuf = NULL;
guchar *dptr;
- guchar *lines[4]; /* Used to expand rows, via rec_outbuf_height,
+ guchar *lines[LINEBUF_SIZE]; /* Used to expand rows, via rec_outbuf_height,
* from the header file:
* " Usually rec_outbuf_height will be 1 or 2,
* at most 4."
@@ -511,6 +512,9 @@ gdk_pixbuf__jpeg_image_load (FILE *f, GError **error)
cinfo.do_fancy_upsampling = FALSE;
cinfo.do_block_smoothing = FALSE;
+ /* batch line updates for efficiency */
+ cinfo.rec_outbuf_height = cinfo.rec_outbuf_height > LINEBUF_SIZE ? cinfo.rec_outbuf_height : LINEBUF_SIZE;
+
pixbuf = gdk_pixbuf_new (GDK_COLORSPACE_RGB,
cinfo.out_color_components == 4 ? TRUE : FALSE,
8, cinfo.output_width, cinfo.output_height);
@@ -738,7 +742,7 @@ gdk_pixbuf__jpeg_image_load_lines (JpegProgContext *context,
GError **error)
{
struct jpeg_decompress_struct *cinfo = &context->cinfo;
- guchar *lines[4];
+ guchar *lines[LINEBUF_SIZE];
guchar **lptr;
guchar *rowptr;
gint nlines, i;
@@ -968,6 +972,9 @@ gdk_pixbuf__jpeg_image_load_increment (gpointer data,
cinfo->do_fancy_upsampling = FALSE;
cinfo->do_block_smoothing = FALSE;
+ /* batch line updates f or efficiency */
+ cinfo->rec_outbuf_height = cinfo.rec_outbuf_height > LINEBUF_SIZE ? cinfo.rec_outbuf_height : LINEBUF_SIZE;
+
if (rc == JPEG_SUSPENDED)
continue;
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