ede/pekwm/PImageLoaderPng.cc

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//
// PImageLoaderPng.cc for pekwm
// Copyright © 2005-2009 Claes Nästén <me@pekdon.net>
//
// This program is licensed under the GNU GPL.
// See the LICENSE file for more information.
//
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif // HAVE_CONFIG_H
#ifdef HAVE_IMAGE_PNG
#include "PImageLoaderPng.hh"
#include <iostream>
extern "C" {
#include <png.h>
}
using std::string;
using std::cerr;
using std::endl;
const int PImageLoaderPng::PNG_SIG_BYTES = 8;
//! @brief PImageLoaderPng constructor.
PImageLoaderPng::PImageLoaderPng(void)
: PImageLoader("PNG")
{
}
//! @brief PImageLoaderPng destructor.
PImageLoaderPng::~PImageLoaderPng(void)
{
}
//! @brief Loads file into data.
//! @param file File to load data from.
//! @param width Set to the width of image.
//! @param height Set to the height of image.
//! @param alpha Set to wheter image has alpha channel.
//! @return Pointer to data on success, else 0.
uchar*
PImageLoaderPng::load(const std::string &file, uint &width, uint &height,
bool &alpha, bool &use_alpha)
{
FILE *fp;
fp = fopen(file.c_str(), "rb");
if (! fp) {
cerr << " *** WARNING: unable to open " << file << " for reading!" << endl;
return 0;
}
if (! checkSignature(fp)) {
cerr << " *** WARNING: " << file << " not a PNG file!" << endl;
fclose(fp);
return 0;
}
// Start PNG loading.
png_structp png_ptr;
png_infop info_ptr;
png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, 0, 0, 0);
if (! png_ptr) {
cerr << " *** ERROR: out of memory, png_create_read_struct failed!" << endl;
fclose(fp);
return 0;
}
info_ptr = png_create_info_struct(png_ptr);
if (! info_ptr) {
cerr << " *** ERROR: out of memory, png_create_info_struct failed!" << endl;
png_destroy_read_struct(&png_ptr, 0, 0);
fclose(fp);
return 0;
}
// Setup error handling.
if (setjmp(png_jmpbuf(png_ptr))) {
png_destroy_read_struct(&png_ptr, &info_ptr, 0);
fclose(fp);
return 0;
}
png_init_io(png_ptr, fp);
png_set_sig_bytes(png_ptr, PImageLoaderPng::PNG_SIG_BYTES);
png_read_info(png_ptr, info_ptr);
int color_type, bpp;
png_uint_32 png_width = 1, png_height = 1;
png_get_IHDR(png_ptr, info_ptr, &png_width, &png_height, &bpp, &color_type, 0, 0, 0);
width = png_width;
height = png_height;
// Setup read information, we want to make sure data get read in
// 16 bit RGB(A)
// palette -> RGB mode
if (color_type == PNG_COLOR_TYPE_PALETTE) {
png_set_palette_to_rgb(png_ptr);
}
// gray -> 8 bit gray
if (color_type == PNG_COLOR_TYPE_GRAY && (bpp < 8)) {
png_set_expand_gray_1_2_4_to_8(png_ptr);
}
if (png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS)) {
png_set_tRNS_to_alpha(png_ptr);
}
if (bpp == 16) {
png_set_strip_16(png_ptr);
}
// gray, gray alpha -> to RGB
if ((color_type == PNG_COLOR_TYPE_GRAY) || (color_type == PNG_COLOR_TYPE_GRAY_ALPHA)) {
png_set_gray_to_rgb(png_ptr);
}
// Now load image data.
uchar *data;
size_t data_size;
png_uint_32 rowbytes, channels;
png_bytepp row_pointers;
png_read_update_info(png_ptr, info_ptr);
rowbytes = png_get_rowbytes(png_ptr, info_ptr);
channels = png_get_channels(png_ptr, info_ptr);
data_size = rowbytes * height / sizeof(uchar);
data = new uchar[data_size];
row_pointers = new png_bytep[height];
for (png_uint_32 y = 0; y < height; ++y) {
row_pointers[y] = data + y * rowbytes;
}
png_read_image(png_ptr, row_pointers);
delete [] row_pointers;
png_read_end(png_ptr, 0);
// Clean up.
png_destroy_read_struct(&png_ptr, &info_ptr, 0);
fclose(fp);
alpha = (channels == 4);
use_alpha = false;
if (alpha) {
uchar *p = data + 3, *end = data + data_size;
for (; p != end && ! use_alpha; p += 4) {
if (*p != 255) {
use_alpha = true;
}
}
}
return data;
}
//! @brief Checks file signature to see if it's a PNG file.
//! @param fp Pointer to open (rb) FILE.
//! @return true if fp is a PNG file, else false.
bool
PImageLoaderPng::checkSignature(FILE *fp)
{
int status;
uchar sig[PImageLoaderPng::PNG_SIG_BYTES];
status = fread(sig, 1, PImageLoaderPng::PNG_SIG_BYTES, fp);
if (status == PImageLoaderPng::PNG_SIG_BYTES) {
return (png_sig_cmp(sig,0,PImageLoaderPng::PNG_SIG_BYTES) == 0);
}
return false;
}
#endif // HAVE_IMAGE_PNG