NAME

asmerge - demonstrates blending of multiple image using different algorithms libAfterImage/tutorials/ASMerge

NAMEASMerge

SYNOPSIS

Scaling and blending of arbitrary number of images using libAfterImage.

DESCRIPTION

We will attempt to interpret command line arguments as sequence of image filenames, geometries and blending types. We'll then try and load all the images, scaling first one to requested size, and blending others at specifyed locations of the first image. We then display the result in simple window. After that we would want to wait, until user closes our window.

New steps described in this tutorial are : Step 1. Layers. Step 2. Merging methods. Step 3. Layer parameters. Step 4. Actual blending of the set of images.

SEE ALSO

Tutorial 1: ASView - explanation of basic steps needed to use
libAfterImage and some other simple things. Tutorial 2: ASScale - image scaling basics. Tutorial 3: ASTile - image tiling and tinting

SOURCE

#include "../afterbase.h" #include "../afterimage.h" #include "common.h"

char *burning_rose[] = {
"asmerge",
"rose512.jpg",
"add",
"back.xpm:512x386",
"hue",
"fore.xpm:512x386" };

void usage() {
printf( "Usage: asmerge [-h]|[image op1 image1 [op2 image2 [...]]]\n");
printf( "Where: image - is background image filename\n");
printf( " image1 - is first overlay's filename\n");
printf( " op1,op2,... - overlay operation."
" Supported operations are :\n");
list_scanline_merging( stdout,
" %-15.15s- %s\n"); }

int main(int argc, char* argv[]) {
Display *dpy = NULL;
ASVisual *asv ;
int screen = 0, depth = 0;
int to_width = 1, to_height = 1;
ASImageLayer *layers ;
int layers_num = 0, i;
ASImage *merged_im ;

/* see ASView.1 : */
set_application_name( argv[0] ); #if (HAVE_AFTERBASE_FLAG==1)
set_output_threshold(OUTPUT_LEVEL_DEBUG); #endif
if( argc == 2 && strncmp(argv[1],"-h", 2) == 0 )
{
usage();
return 0;
}
if( argc <= 3 )
{
show_error( "not enough arguments, please see usage:%s", " ");
usage() ;
printf( "Using the default, \"The Burning Rose\", composition :\n");
printf( "\n\trose512.jpg add back.xpm:512x386 hue "
"fore.xpm:512x386\n");
argv = &(burning_rose[0]) ;
argc = 6;
}

#ifndef X_DISPLAY_MISSING
dpy = XOpenDisplay(NULL);
_XA_WM_DELETE_WINDOW = XInternAtom( dpy, "WM_DELETE_WINDOW", False);
screen = DefaultScreen(dpy);
depth = DefaultDepth( dpy, screen ); #endif
/* see ASView.3 : */
asv = create_asvisual( dpy, screen, depth, NULL );

/* see ASMerge.1 : */
layers = safecalloc( argc/2, sizeof(ASImageLayer) );

for( i = 1 ; i < argc ; i++ )
{
int x = 0, y = 0;
unsigned int width, height ;
int geom_flags = 0 ;
char *separator;
char *filename ;
/* see ASMerge.2 */
if( i > 1 )
{
/* see blend_scanlines_name2func() : */
if((layers[layers_num].merge_scanlines =
blend_scanlines_name2func( argv[i] )) == NULL )
continue ;
if( ++i >= argc )
break;
}
if( (separator = strchr( argv[i], ':' )) != NULL )
{ /* see ASTile.1 : */
geom_flags = XParseGeometry( separator+1,
&x, &y, &width, &height);
filename = mystrndup( argv[i], separator-argv[i] );
}else
filename = argv[i] ;
layers[layers_num].im = file2ASImage( filename, 0xFFFFFFFF,
SCREEN_GAMMA, 100, getenv("IMAGE_PATH"), NULL );
if( filename != argv[i] )
free( filename );
if( layers[layers_num].im != NULL )
{
if( !get_flags(geom_flags, WidthValue) )
width = layers[layers_num].im->width ;
if( !get_flags(geom_flags, HeightValue) )
height = layers[layers_num].im->height ;
/* see ASMerge.3 : */
if( layers[layers_num].merge_scanlines == NULL )
layers[layers_num].merge_scanlines =
alphablend_scanlines ;
layers[layers_num].clip_width = width ;
layers[layers_num].clip_height = height ;
if( layers_num > 0 )
{
layers[layers_num].dst_x = x ;
layers[layers_num].dst_y = y ;
}else
{
to_width = width ;
to_height = height ;
if( width != layers[layers_num].im->width ||
height != layers[layers_num].im->height )
{
ASImage *scaled_bottom ;
/* see ASScale.2 : */
scaled_bottom = scale_asimage( asv,
layers[layers_num].im,
width, height,
False, 100,
ASIMAGE_QUALITY_DEFAULT );
destroy_asimage( &(layers[layers_num].im) );
layers[layers_num].im = scaled_bottom ;
}
}
++layers_num ;
}
}

if( layers_num <= 0 )
{
show_error( "there is no images to merge. Aborting");
return 2;
}

/* see ASMerge.4 */
merged_im = merge_layers( asv, layers, layers_num,
to_width, to_height, #ifndef X_DISPLAY_MISSING
ASA_XImage, #else
ASA_ASImage, #endif
0, ASIMAGE_QUALITY_DEFAULT );
while( --layers_num >= 0 )
destroy_asimage( &(layers[layers_num].im) );
free( layers );

if( merged_im )
{ #ifndef X_DISPLAY_MISSING
/* see ASView.4 : */
Window w = create_top_level_window( asv, DefaultRootWindow(dpy),
32, 32,
to_width, to_height,
1, 0, NULL,
"ASMerge", NULL );
if( w != None )
{
Pixmap p ;

XMapRaised (dpy, w);
/* see ASView.5 : */
p = asimage2pixmap( asv, DefaultRootWindow(dpy), merged_im,
NULL, True );

destroy_asimage( &merged_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
/* writing result into the file */
ASImage2file( merged_im, NULL, "asmerge.jpg", ASIT_Jpeg, NULL );
destroy_asimage( &merged_im ); #endif
} #ifdef DEBUG_ALLOCS
build_xpm_colormap(NULL);
print_unfreed_mem(); #endif
return 0 ; }

libAfterImage/tutorials/ASMerge.1 [4.1]

SYNOPSIS

Step 1. Layers.

DESCRIPTION

libAfterImage performs blending/merging of different images, using arrays of ASImageLayer structures, with first element representing the bottommost image. Each structure specifies exact position on resulting image where overlay should be blended to, tint of the overlay, size, to which overlay should be tiled, overlay's origin, and overlay's background color. Arbitrary number of layers can be merged whithin single run.

Accordingly all that is needed to merge bunch of images is to create array of ASImageLayer structures and fill it up appropriately.

EXAMPLE

layers = safecalloc( argc/2, sizeof(ASImageLayer) );
libAfterImage/tutorials/ASMerge.2 [4.2]

SYNOPSIS

Step 2. Merging methods.

DESCRIPTION

Each layer can be merged in using its own method. There are about 15 different methods implemented in libAfterImage, and user app can implement other methods of its own. To specify method all that is needed is to set merge_scanlines member of ASImageLayer to pointer to the function, implementing specific method.

libAfterImage provides facility to parse method name strings into actuall function pointers. That could be used to simplifi scripting, etc.

EXAMPLE

if((layers[layers_num].merge_scanlines =
blend_scanlines_name2func( argv[i] )) == NULL )
continue ; NOTE All layers MUST have valid merge_scanlines pointer, even the bottommost layer, despite the fact that it has nothing to be merged with. If merge_scanlines is set to NULL - this layer will be ignored. That could be used to turn on/off particular layers.
libAfterImage/tutorials/ASMerge.3 [4.3]

SYNOPSIS

Step 3. Layer parameters.

DESCRIPTION

Several ASImageLayer members are mandatory and cannot be set to 0. Such as : im - image to be merged; clip_width, clip_height - this will be used to tile the image; merge_scanlines - must be set to a pointer to the function implementing merging method. If any of this is set to 0 - then layer will be ignored. The rest of the parameters are optional. Note thou that tint parameter will tint overlay's RGB components and alpha component, as the result it could be used to make opaque images - semitransparent.

EXAMPLE

if( layers[layers_num].merge_scanlines == NULL )
layers[layers_num].merge_scanlines =
alphablend_scanlines ;
layers[layers_num].clip_width = width ;
layers[layers_num].clip_height = height ;
if( layers_num > 0 )
{
layers[layers_num].dst_x = x ;
layers[layers_num].dst_y = y ;
}
libAfterImage/tutorials/ASMerge.4 [4.4]

SYNOPSIS

Step 4. Actual blending of the set of images.

DESCRIPTION

After set of layers has been prepared - it can be passed to merge_layers() function, that will create new ASImage of specifyed size, and then blend all the layers together to fill this image.

EXAMPLE

merged_im = merge_layers( asv, layers, layers_num,
to_width, to_height,
ASA_ASImage, 0,
ASIMAGE_QUALITY_DEFAULT );
while( --layers_num >= 0 )
destroy_asimage( &(layers[layers_num].im) );
free( layers );

NOTES

After we've blended layers - we no longer need ASImageLayer array. So proceeding to clean it up, by destroying overlay AsImages first, and then freeing array itself.

SEE ALSO

merge_asimage().