My guess: you are doing something wrong. I've just compared libjpeg-turbo with gdk.PixbufLoader and found virtually no speed differences. The code I used is below.
For the libjpeg-turbo (jpegload.c):
#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/time.h>
#include <jpeglib.h>
void decompress(FILE* fd)
{
JSAMPARRAY buffer;
int row_stride;
struct jpeg_decompress_struct cinfo;
struct jpeg_error_mgr jerr;
cinfo.err = jpeg_std_error(&jerr);
jpeg_create_decompress(&cinfo);
jpeg_stdio_src(&cinfo, fd);
jpeg_read_header(&cinfo, TRUE);
jpeg_start_decompress(&cinfo);
row_stride = cinfo.output_width * cinfo.output_components;
buffer = (*cinfo.mem->alloc_sarray)
((j_common_ptr) &cinfo, JPOOL_IMAGE, row_stride, 1);
while (cinfo.output_scanline < cinfo.output_height) {
(void) jpeg_read_scanlines(&cinfo, buffer, 1);
}
jpeg_finish_decompress(&cinfo);
jpeg_destroy_decompress(&cinfo);
}
int main(int argc, char** argv)
{
long len;
FILE *fd;
unsigned char *buf;
struct timeval start, end;
int i;
const int N = 100;
int delta;
/* read file to cache it in memory */
assert(argc == 2);
fd = fopen(argv[1], "rb");
fseek(fd, 0, SEEK_END);
len = ftell(fd);
rewind(fd);
buf = malloc(len);
assert(buf != NULL);
assert(fread(buf, 1, len, fd) == len);
gettimeofday(&start, NULL);
for(i = 0; i < N; i++) {
rewind(fd);
decompress(fd);
}
gettimeofday(&end, NULL);
if(end.tv_sec > start.tv_sec) {
delta = (end.tv_sec - start.tv_sec - 1) * 1000;
end.tv_usec += 1000000;
}
delta += (end.tv_usec - start.tv_usec) / 1000;
printf("time spent in decompression: %d msec\n",
delta/N);
}
For python gdk (gdk_load.py):
import sys
import gtk
import time
def decompress(data):
pbl = gtk.gdk.PixbufLoader()
pbl.write(data, len(data))
pbl.close()
return pbl.get_pixbuf()
data = open(sys.argv[1]).read()
N = 100
start = time.time()
for i in xrange(N):
decompress(data)
end = time.time()
print "time spent in decompression: %d msec" % int((end - start) * 1000 / N)
Test run results:
$ gcc jpegload.c -ljpeg
$ ./a.out DSC_8450.JPG
time spent in decompression: 75 msec
$ python gdk_load.py DSC_8450.JPG
time spent in decompression: 75 msec
$ identify DSC_8450.JPG
DSC_8450.JPG JPEG 3008x2000 3008x2000+0+0 8-bit DirectClass 2.626MB 0.000u 0:00.019
EDIT: and another test, using gi.repostiroy this time:
import sys
import time
from gi.repository import GdkPixbuf
def decompress(filename):
pb = GdkPixbuf.Pixbuf.new_from_file(filename)
return pb
N = 100
start = time.time()
for i in xrange(N):
decompress(sys.argv[1])
end = time.time()
print "time spent in decompression: %d msec" % int((end - start) * 1000 / N)
And results:
$ python gi_load.py DSC_8450.JPG
time spent in decompression: 74 msec
GdkPixbuf.PixbufLoader using gi.repository is really much MUCH slower then "pure" gtk.gdk. Code:
import sys
import time
from gi.repository import GdkPixbuf
def decompress(data):
pbl = GdkPixbuf.PixbufLoader()
pbl.write(data, len(data))
pbl.close()
return pbl.get_pixbuf()
data = bytearray(open(sys.argv[1]).read())
N = 100
start = time.time()
for i in xrange(N):
decompress(data)
end = time.time()
print "time spent in decompression: %d msec" % int((end - start) * 1000 / N)
Results:
$ python gi_load.py DSC_8450.JPG
time spent in decompression: 412 msec
But GdkPixbuf.Pixbuf.new_from_file works as fast as pure C version even using gi.repository, so you are still either doing something wrong, or expecting too much.
