C simple scale 2X, pixelate

draw_png_scale2x.c

/* gcc -o demo draw_png_2x.c

# ./demo 8
0000 00
0000 01
1000 02
0000 03
00000000000000000000000000000000 00
00000000000000000000000000000000 01
00000000000000000000000000000000 02
00000000000000000000000000000000 03
11000000000000000000000000000000 04
11000000000000000000000000000000 05
00000000000000000000000000000000 06
00000000000000000000000000000000 07

# ./demo 5
0000 00
0100 01
0001 02
0000 03
00000000000000000000000000000000 00
00000000000000000000000000000000 01
00110000000000000000000000000000 02
00110000000000000000000000000000 03
00000011000000000000000000000000 04
00000011000000000000000000000000 05
00000000000000000000000000000000 06
00000000000000000000000000000000 07

*/

#include <stdio.h>
#include <sys/types.h>
#include <string.h>
#include <stdlib.h>

#define CANVAS_W 32
#define CANVAS_H 8

int32_t canvas[CANVAS_W * CANVAS_H];

#define PNG_W 4
int32_t png[PNG_W * 4];

void print(int32_t *d, int32_t x, int32_t y)
{
    int w, h;
    for(h = 0; h < y; h++)
    {
        for(w = 0; w < x; w++) printf("%x", d[(h * x) + w]);  // (H * CANVAS_W) + W

        printf(" %.2d\n", h);
    }
}

/***********************************************************************
* draw png part into frame.
*
* int32_t idx      =  index of loaded png
* int32_t can_x    =  start x coordinate into canvas
* int32_t can_y    =  start y coordinate into canvas
* int32_t png_x    =  start x coordinate into png
* int32_t png_y    =  start y coordinate into png
* int32_t w        =  width of png part to blit
* int32_t h        =  height of png part to blit
***********************************************************************/
int32_t draw_png(const int32_t idx,
    const int32_t c_x, const int32_t c_y,   // coordinate into canvas
    const int32_t p_x, const int32_t p_y,   // coordinate into png
    const int32_t w,   const int32_t h)     // size of png part to blit
{
    int32_t i, k;
    int32_t *px = NULL, *src = NULL;

    for(i = 0; i < h; i++)
        for(k = 0; k < w; k++)
        {

            if((c_x + k < CANVAS_W) 
            && (c_y + i < CANVAS_H))
            {
//                *px = mix_color(*px,  ctx.png[idx].addr[(p_x + p_y * ctx.png[idx].w) + (k + i * ctx.png[idx].w)]);
                  src = &png[(p_x + p_y * PNG_W) + (k + i * PNG_W)];

//                px = &ctx.canvas[(c_y + i) * CANVAS_W + c_x + k]; // (H * CANVAS_W) + W
                  /*
                  (2* H   ) * CANVAS_W) + 2* W,
                  (2* H   ) * CANVAS_W) + 2* W +1,
                  (2* H +1) * CANVAS_W) + 2* W,
                  (2* H +1) * CANVAS_W) + 2* W +1,
                  */

                  px = &canvas[ 2* (c_y + i)     * CANVAS_W + 2* (c_x + k)   ];  *px = *src;
                  px = &canvas[ 2* (c_y + i)     * CANVAS_W + 2* (c_x + k) +1];  *px = *src;

                  px = &canvas[(2* (c_y + i) +1) * CANVAS_W + 2* (c_x + k)   ];  *px = *src;
                  px = &canvas[(2* (c_y + i) +1) * CANVAS_W + 2* (c_x + k) +1];  *px = *src;

            }
        }

    return (c_x + w);
}


int main(int argc, char *argv[])
{
    memset(&canvas, 0, sizeof(canvas));

    png[atoi(argv[1])] = png[atoi(argv[1]) +PNG_W +2] = 1;

    print(png, PNG_W, 4);

    draw_png(0, 0, 0, 0, 0, 4, 4);

    print(canvas, CANVAS_W, CANVAS_H);

    return 0;
}