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| bool Texture::Load(std::string path)
{
//header for testing if it is a png
png_byte header[8];
//open file as binary
FILE *fp = fopen(path.c_str(), "rb");
if (!fp) {
std::cerr << " Cannot open texture file. " << path << std::endl;
return false;
}
//read the header
fread(header, 1, 8, fp);
//test if png
int is_png = !png_sig_cmp(header, 0, 8);
if (!is_png) {
fclose(fp);
std::cerr << " Image is not a PNG. " << path << std::endl;
return false;
}
//create png struct
png_structp png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL,
NULL, NULL);
if (!png_ptr) {
fclose(fp);
std::cerr << " Error during png_struct creation. " << path << std::endl;
return false;
}
//create png info struct
png_infop info_ptr = png_create_info_struct(png_ptr);
if (!info_ptr) {
png_destroy_read_struct(&png_ptr, (png_infopp) NULL, (png_infopp) NULL);
fclose(fp);
std::cerr << " Error during memory allocation. " << path << std::endl;
return false;
}
//create png info struct
png_infop end_info = png_create_info_struct(png_ptr);
if (!end_info) {
png_destroy_read_struct(&png_ptr, &info_ptr, (png_infopp) NULL);
fclose(fp);
std::cerr << " Error during memory allocation. " << path << std::endl;
return false;
}
//png error stuff, not sure libpng man suggests this.
if (setjmp(png_jmpbuf(png_ptr))) {
png_destroy_read_struct(&png_ptr, &info_ptr, &end_info);
fclose(fp);
std::cerr << " Problem to read file. " << path << std::endl;
return false;
}
//init png reading
png_init_io(png_ptr, fp);
//let libpng know you already read the first 8 bytes
png_set_sig_bytes(png_ptr, 8);
// read all the info up to the image data
png_read_info(png_ptr, info_ptr);
//variables to pass to get info
int bit_depth, color_type;
png_uint_32 twidth, theight;
// get info about png
png_get_IHDR(png_ptr, info_ptr, &twidth, &theight, &bit_depth, &color_type, NULL, NULL, NULL);
//update width and height based on png info
width = twidth;
height = theight;
// Update the png info struct.
png_read_update_info(png_ptr, info_ptr);
// Row size in bytes.
int rowbytes = png_get_rowbytes(png_ptr, info_ptr);
// Allocate the image_data as a big block, to be given to opengl
png_byte *image_data = new png_byte[rowbytes * height];
if (!image_data) {
//clean up memory and close stuff
png_destroy_read_struct(&png_ptr, &info_ptr, &end_info);
std::cerr << " Error during memory allocation. " << path << std::endl;
fclose(fp);
return false;
}
//row_pointers is for pointing to image_data for reading the png with libpng
png_bytep *row_pointers = new png_bytep[height];
if (!row_pointers) {
//clean up memory and close stuff
png_destroy_read_struct(&png_ptr, &info_ptr, &end_info);
delete[] image_data;
fclose(fp);
return false;
}
// set the individual row_pointers to point at the correct offsets of image_data
for (int i = 0; i < height; ++i)
row_pointers[height - 1 - i] = image_data + i * rowbytes;
//read the png into image_data through row_pointers
png_read_image(png_ptr, row_pointers);
//Now generate the OpenGL texture object
glGenTextures(1, &texId);
glBindTexture(GL_TEXTURE_2D, texId);
glTexImage2D(GL_TEXTURE_2D,0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, (GLvoid*) image_data);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
//clean up memory and close stuff
png_destroy_read_struct(&png_ptr, &info_ptr, &end_info);
delete[] image_data;
delete[] row_pointers;
fclose(fp);
return true;
} |
