HI
I know that it is not the appropriate problem for this news group
but maybe someone can tell me where I can ask then:
OK THe problem is that I receive an buffer of data through sockets, and
those data are jpg image (an image compressed using libjpeg).
Now I want to show them using gdk-pixbuf - what I did (in pthread using
libjpeg library to decompress data to rgb image, using gdk-pixbuf to
create pixbuf and show it in drawingarea). OK. Fine but......
When I receive many images it hangs .... so I tracked it down - there is
no problem with GTK, Pixbuf, sockets, but the problem was with libjpeg -
and exactly with function:
jpeg_start_decompress(&cinfo);
I tried to read image from file.jpg (well documented) instead of
decompressing from data in memory but it is still the same problem. Dont
know why - at the beggining it reads fast the file, but after few times
it hangs there (it starts decompressing for ever). I read documentation
for libjpeg library again and it is writen that
jpeg_start_decompress(&cinfo) can be slow however if I do simple
decompressing it should return quickly. So???? I am in .... dont want to
say where :)
OK. Please help.
Zbigniew Wasik
Ps. Here is code:
How I read a file :
int jpg_ReadJpegToRGB_a( char *fname,
int *w_ret, int *h_ret,
unsigned char **rgb_return)
{
static unsigned char *data = NULL;
FILE *fp = NULL;
struct jpeg_decompress_struct cinfo;
JSAMPROW rowptr[1];
my_error_mgr merr;
int w,h,bperpix;
printf(" ReadJPG: 1.0 \n") ;
if((fp = fopen(fname, "r")) == NULL) return 0;
/* Step 1: allocate and initialize JPEG decompression object */
printf(" ReadJPG: 2.0 set err mgr\n") ;
cinfo.err = jpeg_std_error(&merr.pub);
merr.pub.error_exit = jp_error_exit;
merr.pub.output_message = jp_error_output;
printf(" ReadJPG: 3.0 set error mgr\n") ;
if(setjmp(merr.setjmp_buffer))
{
/* jpeg has signaled an error */
jpeg_destroy_decompress(&cinfo);
(void)fclose(fp);
if(data) (void)free(data);
return(0);
}
jpeg_create_decompress(&cinfo);
/* Step 2: specify data source (eg, a file) */
printf(" ReadJPG: 4.0 data source file\n") ;
jpeg_stdio_src(&cinfo, fp);
/* Step 3: read file parameters with jpeg_read_header() */
printf(" ReadJPG: 5.0 header \n") ;
(void) jpeg_read_header(&cinfo, TRUE);
printf(" ReadJPG: 6.0 header \n") ;
jpeg_calc_output_dimensions(&cinfo);
w = cinfo.output_width;
h = cinfo.output_height;
printf(" ReadJPG: 7.0 header \n") ;
bperpix = cinfo.output_components;
if(bperpix != 1 && bperpix != 3)
{
fprintf(stderr, "%s: can't read %d-plane JPEG file.",
fname, cinfo.output_components);
jpeg_destroy_decompress(&cinfo);
fclose(fp);
return 0;
}
printf(" ReadJPG: 8.0 malloc\n") ;
if((data = (unsigned char *)malloc( 4 * w * h *
sizeof(unsigned char))) == NULL)
{
jpeg_destroy_decompress(&cinfo);
fclose(fp);
fprintf(stderr,"ReadJPEG");
return 0;
}
/* Step 4: set parameters for decompression */
printf(" ReadJPG: 9.0 start decompress\n") ;
jpeg_start_decompress(&cinfo);
/* Step 5: decompress */
printf(" ReadJPG: 10.0 decompress\n") ;
while(cinfo.output_scanline < cinfo.output_height)
{
rowptr[0] = (JSAMPROW) &data[cinfo.output_scanline * w * bperpix];
(void) jpeg_read_scanlines(&cinfo, rowptr, (JDIMENSION) 1);
}
printf(" ReadJPG: 11.0 isGray\n") ;
if(cinfo.jpeg_color_space == JCS_GRAYSCALE)
{
unsigned char *t1, *t2, c;
int i,j;
t1 = data;
t2 = t1 + 3* w * h;
memcpy(t2, t1, w * h);
for(i = 0; i < h; i++)
for(j = 0; j < w; j++)
{
c = *t2++;
*t1++ = c; *t1++ = c; *t1++ = c;
}
}
/* Step 6: clean up */
printf(" ReadJPG: 12.0 Clean up\n") ;
jpeg_finish_decompress(&cinfo);
jpeg_destroy_decompress(&cinfo);
fclose(fp);
/* finally .... */
printf(" ReadJPG: 13.0 Final\n") ;
*w_ret = w;
*h_ret = h;
if(rgb_return)
{
*rgb_return = data;
return(1);
}
fprintf(stderr, "Wrong pointer to rgb buffer \n") ;
return(0);
}
How I use it (more or less):
void main_thread() {
isRUnning = TRUE ;
while(isRunning) {
g_print(" Showing in thread \n") ;
/* It grabs one image (what image depends on command) */
jpg_ReadJpegToRGB_a("rose.jpg",&(client->width),&(client->height),
&(client->rgbBuffer)) ;
/* Now let show the image */
rgbViewer_showImage(client->source,
client->rgbBuffer,
client->width,client->height) ;
sleep(5) ; // just for debugging now 5 seconds
} // end of while
}
SORRY FOR MESS
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