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asscale - demonstrates image loading and scaling libAfterImage/tutorials/ASScale
Contents
Description
scale_asimage() scales image both up and down, and is very easy to use - just pass it new size. In this
example we use default quality. Default is equivalent to GOOD which should be sufficient in most cases.
Compression is set to 0 since we do not intend to store image for long time. Even better - we don't need
to store it at all - all we need is XImage, so we can transfer it to the server easily. That is why
to_xim argument is set to ASA_XImage. As the result obtained ASImage will not have any data in its
buffers, but it will have ximage member set to point to valid XImage. Subsequently we enjoy that
convenience, by setting use_cached to True in call to asimage2pixmap. That ought to save us a lot of
processing.
Scaling algorithm is rather sophisticated and is implementing 4 point interpolation. Which basically
means that we try to approximate each missing point as an extension of the trend of 4 neighboring points
- two on each side. Closest neighbor's have more weight then outside ones. 2D scaling is performed by
scaling each scanline first, and then interpolating missing scanlines. Scaling down is somewhat
skimpier, as it amounts to simple averaging of the multiple pixels. All calculations are done in integer
math on per channel basis, and with precision 24.8 bits per channel per pixel.
Example
scaled_im = scale_asimage( asv, im, to_width, to_height,
ASA_XImage, 0, ASIMAGE_QUALITY_DEFAULT );
destroy_asimage( &im );
Name
asscale - demonstrates image loading and scaling libAfterImage/tutorials/ASScale
Nameasscale
Notes
Scaling image up to very large height is much slower then to same width due to algorithm specifics. Yet
even on inferior hardware it yields decent speeds. When we successfully scaled image - we no longer need
the original - getting rid of it so it does not clog memory.
See Also
scale_asimage().
3rd Berkeley Distribution AfterStep v.2.2.12 asscale(3x)
Source
#include "../afterbase.h" #include "../afterimage.h" #include "common.h"
void usage() {
printf( "Usage: asscale [-h]|[image [WIDTH[xHEIGHT]]]\n");
printf( "Where: image - is image filename.\n");
printf( " WIDTH - width to scale image to.( Naturally :)\n");
printf( " HEIGHT- height to scale image to.\n"); }
int main(int argc, char* argv[]) {
char *image_file = "rose512.jpg" ;
int dummy, geom_flags = 0;
unsigned int to_width, to_height ;
ASImage *im ;
int clip_x = 0, clip_y = 0, clip_width = 0, clip_height = 0 ;
int slice_x_start = 0, slice_x_end = 0, slice_y_start = 0, slice_y_end = 0 ;
Bool slice_scale = False ;
Display *dpy = NULL;
/* see ASView.1 : */
set_application_name( argv[0] );
if( argc > 1 )
{
int i = 2;
if( strncmp( argv[1], "-h", 2 ) == 0 )
{
usage();
return 0;
}
image_file = argv[1] ;
if( argc > 2 ) /* see ASScale.1 : */
geom_flags = XParseGeometry( argv[2], &dummy, &dummy,
&to_width, &to_height );
while( ++i < argc )
{
if( strncmp( argv[i], "-sx1", 4 ) == 0 && i+1 < argc )
slice_x_start = atoi(argv[++i]) ;
else if( strncmp( argv[i], "-sx2", 4 ) == 0 && i+1 < argc )
slice_x_end = atoi(argv[++i]) ;
else if( strncmp( argv[i], "-sy1", 4 ) == 0 && i+1 < argc )
slice_y_start = atoi(argv[++i]) ;
else if( strncmp( argv[i], "-sy2", 4 ) == 0 && i+1 < argc )
slice_y_end = atoi(argv[++i]) ;
else if( strncmp( argv[i], "-cx", 4 ) == 0 && i+1 < argc )
clip_x = atoi(argv[++i]) ;
else if( strncmp( argv[i], "-cy", 4 ) == 0 && i+1 < argc )
clip_y = atoi(argv[++i]) ;
else if( strncmp( argv[i], "-cwidth", 7 ) == 0 && i+1 < argc )
clip_width = atoi(argv[++i]) ;
else if( strncmp( argv[i], "-cheight", 8 ) == 0 && i+1 < argc )
clip_height = atoi(argv[++i]) ;
else if( strncmp( argv[i], "-ss", 3 ) == 0 )
slice_scale = True ;
}
}else
{
show_warning( "no image file or scale geometry - defaults used:"
" \"%s\" ",
image_file );
usage();
}
/* see ASView.2 : */
im = file2ASImage( image_file, 0xFFFFFFFF, SCREEN_GAMMA, 0, getenv("IMAGE_PATH"), NULL );
if( im != NULL )
{
ASVisual *asv ;
ASImage *scaled_im ;
/* Making sure tiling geometry is sane : */
if( !get_flags(geom_flags, WidthValue ) )
to_width = im->width*2 ;
if( !get_flags(geom_flags, HeightValue ) )
to_height = im->height*2;
printf( "%s: scaling image \"%s\" to %dx%d by factor of %fx%f\n",
get_application_name(), image_file, to_width, to_height,
(double)to_width/(double)(im->width),
(double)to_height/(double)(im->height) );
#ifndef X_DISPLAY_MISSING
{
Window w ;
int screen, depth ;
dpy = XOpenDisplay(NULL);
_XA_WM_DELETE_WINDOW = XInternAtom( dpy,
"WM_DELETE_WINDOW",
False);
screen = DefaultScreen(dpy);
depth = DefaultDepth( dpy, screen );
/* see ASView.3 : */
asv = create_asvisual( dpy, screen, depth, NULL );
/* see ASView.4 : */
w = create_top_level_window( asv, DefaultRootWindow(dpy),
32, 32,
to_width, to_height, 1, 0, NULL,
"ASScale", image_file );
if( w != None )
{
Pixmap p ;
XMapRaised (dpy, w);
/* see ASScale.2 : */
if( slice_x_start == 0 && slice_x_end == 0 &&
slice_y_start == 0 && slice_y_end == 0 )
{
scaled_im = scale_asimage2( asv, im,
clip_x, clip_y, clip_width, clip_height,
to_width, to_height,
ASA_XImage, 0,
ASIMAGE_QUALITY_DEFAULT );
}else
{
scaled_im = slice_asimage2( asv, im, slice_x_start, slice_x_end,
slice_y_start, slice_y_end,
to_width, to_height, slice_scale,
ASA_XImage, 0,
ASIMAGE_QUALITY_DEFAULT );
}
destroy_asimage( &im );
/* see ASView.5 : */
p = asimage2pixmap(asv, DefaultRootWindow(dpy), scaled_im,
NULL, True );
/* print_storage(NULL); */
destroy_asimage( &scaled_im );
/* see common.c: set_window_background_and_free() : */
p = set_window_background_and_free( w, p );
}
/* see common.c: wait_closedown() : */
wait_closedown(w);
dpy = NULL;
} #else
asv = create_asvisual( NULL, 0, 0, NULL );
scaled_im = scale_asimage(asv, im, to_width, to_height,
ASA_ASImage, 0,
ASIMAGE_QUALITY_DEFAULT );
/* writing result into the file */
ASImage2file( scaled_im, NULL, "asscale.jpg", ASIT_Jpeg, NULL );
destroy_asimage( &scaled_im );
destroy_asimage( &im ); #endif
}
return 0 ; }
libAfterImage/tutorials/ASScale.1 [2.1]
Synopsis
Step 2. Actual scaling the image.
PNG Icons
