Ladda PNG

bool Image::loadPNG(const char *fileName){
	png_structp png_ptr = NULL;
	png_infop info_ptr = NULL;
    FILE *file;

    png_byte pbSig[8];
    int iBitDepth, iColorType;
    png_byte **ppbRowPointers;

    // open the PNG input file
    if ((file = fopen(fileName, "rb")) == NULL) return false;

    // first check the eight byte PNG signature
    fread(pbSig, 1, 8, file);
    if (!png_check_sig(pbSig, 8)){
		fclose(file);
		return false;
	}

    // create the two png(-info) structures
    if ((png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, (png_error_ptr) NULL, (png_error_ptr) NULL)) == NULL){
		fclose(file);
        return false;
    }

    if ((info_ptr = png_create_info_struct(png_ptr)) == NULL){
        png_destroy_read_struct(&png_ptr, NULL, NULL);
		fclose(file);
        return false;
    }

	// initialize the png structure
	png_init_io(png_ptr, file);
	png_set_sig_bytes(png_ptr, 8);
	
	// read all PNG info up to image data
	png_read_info(png_ptr, info_ptr);
	
	// get width, height, bit-depth and color-type
	png_get_IHDR(png_ptr, info_ptr, (png_uint_32 *) &width, (png_uint_32 *) &height, &iBitDepth, &iColorType, NULL, NULL, NULL);
	
	depth = 1;
	nMipMaps = 1;

	int nChannels = png_get_channels(png_ptr, info_ptr);
	switch (nChannels){
		case 1:
			format = FORMAT_I8;
			break;
		case 3:
			format = FORMAT_RGB8;
			break;
		case 4:
			format = FORMAT_RGBA8;
			break;
	}

	int rowSize = width * nChannels * iBitDepth / 8;

	// now we can allocate memory to store the image
	pixels = new unsigned char[rowSize * height];
	
	// set the individual row-pointers to point at the correct offsets
	ppbRowPointers = new png_bytep[height];
	for (int i = 0; i < height; i++)
		ppbRowPointers[i] = pixels + i * rowSize;
	
	// now we can go ahead and just read the whole image
	png_read_image(png_ptr, ppbRowPointers);
	
	// read the additional chunks in the PNG file (not really needed)
	png_read_end(png_ptr, NULL);
	
	delete ppbRowPointers;

	if (iColorType == PNG_COLOR_TYPE_PALETTE){
		png_colorp palette;
		int num_palette;
		png_get_PLTE(png_ptr, info_ptr, &palette, &num_palette);

		unsigned char *newPixels = new unsigned char[width * height * 3];
		if (iBitDepth == 4){
			for (int i = 0; i < rowSize * height; i++){
				unsigned int i0 = pixels[i] >> 4;
				unsigned int i1 = pixels[i] & 0xF;
				newPixels[6 * i    ] = palette[i0].red;
				newPixels[6 * i + 1] = palette[i0].green;
				newPixels[6 * i + 2] = palette[i0].blue;
				newPixels[6 * i + 3] = palette[i1].red;
				newPixels[6 * i + 4] = palette[i1].green;
				newPixels[6 * i + 5] = palette[i1].blue;
			}
		} else {
			for (int i = 0; i < rowSize * height; i++){
				newPixels[3 * i    ] = palette[pixels[i]].red;
				newPixels[3 * i + 1] = palette[pixels[i]].green;
				newPixels[3 * i + 2] = palette[pixels[i]].blue;
			}
		}
		format = FORMAT_RGB8;

		delete pixels;
		pixels = newPixels;
	}


	// and we're done
    png_destroy_read_struct(&png_ptr, &info_ptr, NULL);

    fclose(file);

    return true;
}