rgbaindexedpng2osd.c

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#include <stdio.h>
#include <stdlib.h>
#include <malloc.h>
#include <unistd.h>	/* isatty() */
#include "png.h"	/* libpng header file:  includes zlib.h and setjmp.h */

static void rgbtoyuv(double R,double G,double B,double *y,double *u,double *v)
{
	*y=(0.257*R + 0.504*G + 0.098*B) + 16.0;
	*u=(-0.148*R - 0.291*G + 0.439*B) + 128.0;
	*v=(0.439*R - 0.368*G - 0.071*B) + 128.0;
}

int main(int argc,char **argv)
{
	FILE *infile;
	FILE *outfile;
	
	png_structp png_ptr;
	png_infop info_ptr;
	png_uint_32 width, height, rowbytes;
	int bit_depth, color_type, num_palette,num_trans;
	png_colorp palette;
	png_bytep alphapalette;
	png_bytep image_data = NULL;
	png_bytepp row_pointers = NULL;
	int i,x,y, size;
	unsigned char b;
	
	if (argc > 1) {
		if ((infile = fopen(argv[1], "rb")) == (FILE *)NULL) {
			fprintf(stderr,
				"rgbaindexedpng2osd error:  cannot open %s for reading\n", argv[1]);
			return 1;
		}
		if ((outfile = fopen(argv[2], "wb")) == (FILE *)NULL) {
			fprintf(stderr,
				"rgbaindexedpng2osd error:  cannot open %s for writing\n", argv[2]);
			return 1;
		}
	}
	else {
		fprintf(stderr,"Usage: %s inputrgbaindexed.png outfile.osd\n",argv[0]);
		return -1;
	}

	png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING,
					 NULL,NULL, NULL);
	info_ptr = png_create_info_struct(png_ptr);

	png_init_io(png_ptr, infile);
	
	png_read_info(png_ptr, info_ptr);  /* read all PNG info up to image data */

	png_get_IHDR(png_ptr, info_ptr, &width, &height, &bit_depth, &color_type,
		     NULL, NULL, NULL);
	
	printf("Reading %ldx%ld image.\n",width,height);
	
	/* writes osd header */
	b = 0x3e;
	fwrite(&b, 1, 1, outfile);
	size = width * height + 1032;
	b = size >> 16;
	fwrite(&b, 1, 1, outfile);
	b = (size >> 8) & 0xff;
	fwrite(&b, 1, 1, outfile);
	b = size & 0xff;
	fwrite(&b, 1, 1, outfile);
	b = width >> 8;
	fwrite(&b, 1, 1, outfile);
	b = width & 0xff;
	fwrite(&b, 1, 1, outfile);
	b = height >> 8;
	fwrite(&b, 1, 1, outfile);
	b = height & 0xff;
	fwrite(&b, 1, 1, outfile);
	/* end of osd header */

	if (color_type != PNG_COLOR_TYPE_PALETTE) {
		fprintf(stderr, "image has a wrong palette type\n");
		return 1;
	}
	png_get_PLTE(png_ptr, info_ptr, &palette, &num_palette);

	// (Manu) what is the last parameter?
	png_get_tRNS(png_ptr, info_ptr, &alphapalette,&num_trans,NULL);
	
	if (num_palette != num_trans) {
		fprintf(stderr, "incorrect palettes: color entries = %d, trans entries = %d\n", num_palette, num_trans);
		return 1;
	}
	if (num_palette>256) {
		fprintf(stderr, "palette size is too big\n");
		return 1;
	}
	/* writes the palette */
	for (i=0 ; i<256 ; i++) {
		double R,G,B,y,u,v;
		int a;
		
		if (i<num_palette) {
			R=palette[i].red;
			G=palette[i].green;
			B=palette[i].blue;
			rgbtoyuv(R,G,B,&y,&u,&v);
			a = alphapalette[i];
		}
		else {
			y = 0;
			u = 0;
			v = 0;
			a = 0;
		}
		
		b = (unsigned char) a;
		fwrite(&b, 1, 1, outfile);
		b = (unsigned char) y;
		fwrite(&b, 1, 1, outfile);
		b = (unsigned char) u;
		fwrite(&b, 1, 1, outfile);
		b = (unsigned char) v;
		fwrite(&b, 1, 1, outfile);
	}
	/* end of osd palette */

	/* allocate space for the PNG image data */
	rowbytes = png_get_rowbytes(png_ptr, info_ptr);
	image_data = (png_bytep)malloc(rowbytes*height);

	row_pointers = (png_bytepp)malloc(height*sizeof(png_bytep));
	
	/* set the individual row_pointers to point at the correct offsets */
	for (i = 0;  i < (int)height;  ++i)
		row_pointers[i] = image_data + i*rowbytes;
	
	png_read_image(png_ptr, row_pointers);   /* read whole image... */
	png_read_end(png_ptr, NULL);             /* ...done! */

	/* writes the indexed image */
	for (y=0;y<(int)height;y++) {
		for (x=0;x<(int)width;x++) {
			b = (unsigned char) ((row_pointers[y])[x]);
			fwrite(&b, 1, 1, outfile);
		}
	}
	/* end of indexed image */

	png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
	free(image_data);
	free(row_pointers);

	fclose(infile);
	fclose(outfile);
		
	printf("Done.\n");
	
	return 0;
}