png2argb.c

#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdarg.h>
#define PNG_DEBUG 3
#include <png.h>

int argb(int a, int r, int g, int b)
{
    int argb = a;

    argb = (argb << 8) + r;
    argb = (argb << 8) + g;
    argb = (argb << 8) + b;

    return argb;
}

void __err(const char *s, ...)
{
    va_list args;
    va_start(args, s);
    vfprintf(stderr, s, args);
    fprintf(stderr, "\n");
    va_end(args);
}

int x, y;

int width, height;
png_byte color_type;
png_byte bit_depth;

png_structp png_ptr;
png_infop info_ptr;
int number_of_passes;
png_bytep *row_pointers;

void process_file()
{
    int file_color_type = png_get_color_type(png_ptr, info_ptr);

    if (file_color_type != PNG_COLOR_TYPE_RGB
        && file_color_type != PNG_COLOR_TYPE_RGBA
        // && file_color_type != PNG_COLOR_TYPE_PALETTE
    ) {
        __err("Color_type of input file must be PNG_COLOR_TYPE_RGB (%d)"
              " or PNG_COLOR_TYPE_RGBA (%d)"
              // " or PNG_COLOR_TYPE_PALETTE (%d)"
              ", (is %d)",
              PNG_COLOR_TYPE_RGB,
              PNG_COLOR_TYPE_RGBA,
              // PNG_COLOR_TYPE_PALETTE,
              png_get_color_type(png_ptr, info_ptr));
    }

    printf("\n\t%d, %d,\n\t", width, height);

    for (y = 0; y < height; y++) {
        png_byte *row = row_pointers[y];

        for (x = 0; x < width; x++) {
            png_byte *ptr;

            if (file_color_type == PNG_COLOR_TYPE_RGBA) { // RGBA
                ptr = &(row[x*4]);
                printf("%d, ", argb(ptr[3], ptr[0], ptr[1], ptr[2]));
            } else { // RGB
                ptr = &(row[x*3]);
                printf("%d, ", argb(255, ptr[0], ptr[1], ptr[2]));
            }

            /* set red value to 0 and green value to the blue one */
            ptr[0] = 0;
            ptr[1] = ptr[2];
        }
    }

    printf("\n");
}

void read_png_file(char *file_name)
{
    FILE *fp;
    unsigned char header[8];

    /* open file and test for it being a png */
    if (file_name == NULL)
        fp = stdin;
    else
        fp = fopen(file_name, "rb");

    if (!fp) {
        __err("File %s could not be opened for reading", file_name);
        return;
    }

    fread(header, 1, 8, fp);
    if (png_sig_cmp(header, 0, 8)) {
        __err("File %s is not recognized as a PNG file", file_name);
    }

    /* initialize stuff */
    png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);

    if (!png_ptr) {
        __err("png_create_read_struct failed");
    }

    info_ptr = png_create_info_struct(png_ptr);
    if (!info_ptr) {
        __err("png_create_info_struct failed");
    }

    if (setjmp(png_jmpbuf(png_ptr))) {
        __err("Error during init_io");
    }

    png_init_io(png_ptr, fp);
    png_set_sig_bytes(png_ptr, 8);

    png_read_info(png_ptr, info_ptr);

    width = png_get_image_width(png_ptr, info_ptr);
    height = png_get_image_height(png_ptr, info_ptr);

    /* read file */
    if (setjmp(png_jmpbuf(png_ptr))) {
        __err("Error during read_image");
    }

    row_pointers = (png_bytep*)malloc(sizeof(png_bytep) * height);
    for (y = 0; y < height; y++) {
        row_pointers[y] = (png_byte*)malloc(png_get_rowbytes(png_ptr, info_ptr));
    }

    png_read_image(png_ptr, row_pointers);

    if (file_name != NULL)
        fclose(fp);

    process_file();
}

int main(int argc, char **argv)
{
    int l;

    if (isatty(fileno(stdin)) && argc < 2) { // NULL stdin, no arguments
        __err("\n  Usage: %s image.png [image2.png] > buffer.argb\n"
              "     or: cat image.png | %s > buffer.argb\n"
              "     or: cat image.png | %s image2.png > buffer.argb\n"
              , argv[0], argv[0], argv[0]);
        return EXIT_FAILURE;
    }

    /* Output the buffer code... */
    printf("unsigned long buffer[] = {");

    /* Process the stdin data */
    if (!isatty(fileno(stdin))) {
        read_png_file(NULL);
    }

    /* Go over the arguments and */
    /* read them as PNG files */
    for (l = 1; l < argc; l++) {
        read_png_file(argv[l]);
    }

    printf("};\n");

    return EXIT_SUCCESS;
}