// Saves a bitmap as tga file
BOOL bmap_savetga (BMAP* b, char* filename)
{
    BOOL bSuccess = false;

    if (b && filename && strlen(filename) > 0)
    {
        var fh = file_open_write(filename);
        if (fh)
        {
            int height = b->height;
            int width = b->width;

            var format = bmap_lock(b, 0);

            // if the bitmap has an alpha channel
            BOOL bAlpha = (((format == 8888) || (format == 1555) || (format == 4444)) && (b->bytespp == 4));

            // header

            int i;
            for (i = 0; i < 2; i++)
                file_asc_write(fh, 0);

            file_asc_write(fh, 2); // uncompressed

            for (i = 0; i < 7; i++)
                file_asc_write(fh, 0);

            // y origin (lower left corner)
            file_asc_write(fh, height & 255);
            file_asc_write(fh, (height >> 8) & 255);

            file_asc_write(fh, width & 255);
            file_asc_write(fh, (width >> 8) & 255);

            file_asc_write(fh, height & 255);
            file_asc_write(fh, (height >> 8) & 255);
            
            int bypp = 24;
            if (bAlpha)
                bypp = 32;

            file_asc_write(fh, bypp); // bypp
            file_asc_write(fh, 0);

            // pixels

            COLOR bgr;
            var alpha;

            int ix, iy;
            for (iy = 0; iy < height; iy++)
            {
                for (ix = 0; ix < width; ix++)
                {
                    // retrieve BGR color and alpha
                    pixel_to_vec(&bgr, &alpha, format, pixel_for_bmap(b, ix, height - 1 - iy));

                    file_asc_write(fh, bgr.blue); // b
                    file_asc_write(fh, bgr.green); // g
                    file_asc_write(fh, bgr.red); // r

                    if (bAlpha)
                        file_asc_write(fh, alpha * 2.55); // a
                }
            }

            // done!
            bmap_unlock(b);
            file_close(fh);

            bSuccess = true;
        }
    }

    return(bSuccess);
}

#include <acknex.h>
#include <default.c>

int main ()
{
    wait(3);
    
    int format = 8888;
    BMAP* b = bmap_createblack(100, 200, format);
    
    bmap_lock(b, 0);
    
    // create red to green gradient from left to right
    // and alpha gradient from translucent to solid from up to bottom
    
    int ix, iy;
    for (ix = 0; ix < b->width; ix++)
    {
        for (iy = 0; iy < b->height; iy++)
        {
            double fx = (double)ix / (double)(b->width-1);
            double fy = (double)iy / (double)(b->height-1);
            
            VECTOR color;
            vec_lerp(&color, COLOR_RED, COLOR_GREEN, fx);
            
            var pixel = pixel_for_vec(&color, 100 * fy, format);
            
            pixel_to_bmap(b, ix, iy, pixel);
        }
    }
    
    bmap_unlock(b);
    
    // save to file
    bmap_savetga(b, "b.tga");
    
    // load from file to compare
    BMAP* bf = bmap_create("b.tga");
    
    video_set(32+b->width+16+bf->width+32, 32+maxv(b->height, bf->height)+32, 0, 2);
    
    while (1)
    {
        draw_text("engine", 32, 32, COLOR_WHITE);
        draw_quad(b, vector(32, 48, 0), NULL, NULL, NULL, NULL, 100, 0);
        
        draw_text("file", 32 + b->width + 16, 32, COLOR_WHITE);
        draw_quad(bf, vector(32 + b->width + 16, 48, 0), NULL, NULL, NULL, NULL, 100, 0);
        
        wait(1);
    }
}