2011-06-05 06:58:47 +03:00
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// Written by Maarten ter Huurne in 2011.
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// Based on the libpng example.c source, with some additional inspiration
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// from SDL_image and openMSX.
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// License: GPL version 2 or later.
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2011-03-30 04:21:31 +03:00
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#include "imageio.h"
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2011-06-05 06:58:47 +03:00
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#include "debug.h"
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#include <SDL.h>
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#include <png.h>
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#include <cassert>
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2011-03-30 04:21:31 +03:00
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2011-06-02 07:19:21 +03:00
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SDL_Surface *loadPNG(const std::string &path) {
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2011-06-05 06:58:47 +03:00
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// Declare these with function scope and initialize them to NULL,
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// so we can use a single cleanup block at the end of the function.
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SDL_Surface *surface = NULL;
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FILE *fp = NULL;
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png_structp png = NULL;
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png_infop info = NULL;
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// Create and initialize the top-level libpng struct.
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png = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
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if (!png) goto cleanup;
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// Create and initialize the image information struct.
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info = png_create_info_struct(png);
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if (!info) goto cleanup;
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// Setup error handling for errors detected by libpng.
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if (setjmp(png_jmpbuf(png))) {
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// Note: This gets executed when an error occurs.
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if (surface) {
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SDL_FreeSurface(surface);
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surface = NULL;
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}
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goto cleanup;
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2011-06-02 07:19:21 +03:00
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}
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2011-06-05 06:58:47 +03:00
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// Open input file.
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fp = fopen(path.c_str(), "rb");
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if (!fp) goto cleanup;
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// Set up the input control if you are using standard C streams.
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png_init_io(png, fp);
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// The call to png_read_info() gives us all of the information from the
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// PNG file before the first IDAT (image data chunk).
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png_read_info(png, info);
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png_uint_32 width, height;
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int bitDepth, colorType;
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png_get_IHDR(
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png, info, &width, &height, &bitDepth, &colorType, NULL, NULL, NULL);
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// Select ARGB pixel format:
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// (ARGB is the native pixel format for the JZ47xx frame buffer in 24bpp)
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// - strip 16 bit/color files down to 8 bits/color
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png_set_strip_16(png);
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// - convert 1/2/4 bpp to 8 bpp
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png_set_packing(png);
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// - expand paletted images to RGB
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// - expand grayscale images of less than 8-bit depth to 8-bit depth
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// - expand tRNS chunks to alpha channels
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png_set_expand(png);
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// - convert grayscale to RGB
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png_set_gray_to_rgb(png);
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// - add alpha channel
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png_set_add_alpha(png, 0xFF, PNG_FILLER_AFTER);
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// - convert RGBA to ARGB
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if (SDL_BYTEORDER == SDL_BIG_ENDIAN) {
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png_set_swap_alpha(png);
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2011-06-02 07:19:21 +03:00
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} else {
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2011-06-05 06:58:47 +03:00
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png_set_bgr(png); // BGRA in memory becomes ARGB in register
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}
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// Update the image info to the post-conversion state.
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png_read_update_info(png, info);
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png_get_IHDR(
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png, info, &width, &height, &bitDepth, &colorType, NULL, NULL, NULL);
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assert(bitDepth == 8);
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assert(colorType == PNG_COLOR_TYPE_RGB_ALPHA);
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// Refuse to load outrageously large images.
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if (width > 65536) {
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WARNING("Refusing to load image because it is too wide\n");
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goto cleanup;
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2011-06-02 07:19:21 +03:00
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}
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2011-06-05 06:58:47 +03:00
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if (height > 2048) {
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WARNING("Refusing to load image because it is too high\n");
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goto cleanup;
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}
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// Allocate ARGB surface to hold the image.
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surface = SDL_CreateRGBSurface(
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SDL_SWSURFACE | SDL_SRCALPHA, width, height, 32,
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0x00FF0000, 0x0000FF00, 0x000000FF, 0xFF000000
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);
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if (!surface) {
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// Failed to create surface, probably out of memory.
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goto cleanup;
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}
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// Compute row pointers.
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png_bytep rowPointers[height];
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for (png_uint_32 y = 0; y < height; y++) {
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rowPointers[y] =
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static_cast<png_bytep>(surface->pixels) + y * surface->pitch;
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}
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// Read the entire image in one go.
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png_read_image(png, rowPointers);
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// Read rest of file, and get additional chunks in the info struct.
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// Note: We got all we need, so skip this step.
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//png_read_end(png, info);
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cleanup:
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// Clean up.
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png_destroy_read_struct(&png, &info, NULL);
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if (fp) fclose(fp);
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return surface;
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2011-03-30 04:21:31 +03:00
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}
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