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asscale

Section: AfterStep X11 window manager (1)
Updated: AfterStep v.2.2.2
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NAME

asscale - demonstrates image loading and scalinglibAfterImage/tutorials/ASScale

NAMEASScale

SYNOPSIS

Simple program based on libAfterImage to scale an image.

DESCRIPTION

We will load image and scale it up to new size, specified as commandline argumentsWe then display the result in simple window.After that we would want to wait, until user closes our window.In this tutorial we will only explain new steps, not described inprevious tutorial. New steps described in this tutorial are :ASScale.1. Parsing geometry spec.ASScale.2. Scaling ASImage.

SOURCE

Source :

#include "../afterbase.h"#include "../afterimage.h"#include "common.h"void usage(){    printf( "Usage: asscale [-h]|[image [WIDTH[xHEIGHT]]]);    printf( "Where: image - is image filename.);    printf( "       WIDTH - width to scale image to.( Naturally :));    printf( "       HEIGHT- height to scale image to.);}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 ;    /* 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:"                      "                       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                 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_ASImage, 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);        }#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 ;}

SYNOPSIS

Step 1. Parsing the geometry.

DESCRIPTION

Geometry can be specified in WIDTHxHEIGHT+X+Y format. Accordingly weuse standard X function to parse it: XParseGeometry. Returned flagstell us what values has been specified. Since we only need size -we check if it is specified and if not - simply default it to twiceas big as original image. Accordingly we use dummy variable to passto XParseGeometry.

EXAMPLE

    geom_flags = XParseGeometry( argv[3], &dummy, &dummy,                                 &to_width, &to_height );

SYNOPSIS

Step 2. Actual scaling the image.

DESCRIPTION

scale_asimage() scales image both up and down, and is very easy touse - just pass it new size. In this example we use default quality.Default is equivalent to GOOD which should be sufficient inmost cases. Compression is set to 0 since we do not intend to storeimage 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 obtainedASImage will not have any data in its buffers, but it will haveximage member set to point to valid XImage. Subsequently we enjoythat convenience, by setting use_cached to True in call toasimage2pixmap. That ought to save us alot of processing.Scaling algorithm is rather sophisticated and is implementing 4 pointinterpolation. Which basically means that we try to approximate eachmissing point as an extension of the trend of 4 neighboring points -two on each side. Closest neighbor's have more weight then outsideones. 2D scaling is performed by scaling each scanline first, andthen interpolating missing scanlines.Scaling down is somewhat skimpier, as it amounts to simple averagingof the multiple pixels. All calculations are done in integer math onper 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 );

NOTES

Scaling image up to very large height is much slower then to samewidth due to algorithm specifics. Yet even on inferior hardware ityields decent speeds.When we successfully scaled image - we no longer need the original -getting rid of it so it does not clog memory.

This document was created byman2html,using the manual pages.

asscale

NAME

NAMEASScale

SYNOPSIS

DESCRIPTION

SEE ALSO

SOURCE

SYNOPSIS

DESCRIPTION

EXAMPLE

SYNOPSIS

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EXAMPLE

NOTES

SEE ALSO

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