Name: Anonymous 2014-08-27 21:56
Good Language:
C/C++:
texture = png_texture_load file_nameC/C++:
GLuint png_texture_load(const char * file_name, int * width, int * height)
{
png_byte header[8];
FILE *fp = fopen(file_name, "rb");
if (fp == 0)
{
perror(file_name);
return 0;
}
// read the header
fread(header, 1, 8, fp);
if (png_sig_cmp(header, 0, 8))
{
fprintf(stderr, "error: %s is not a PNG.\n", file_name);
fclose(fp);
return 0;
}
png_structp png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
if (!png_ptr)
{
fprintf(stderr, "error: png_create_read_struct returned 0.\n");
fclose(fp);
return 0;
}
// create png info struct
png_infop info_ptr = png_create_info_struct(png_ptr);
if (!info_ptr)
{
fprintf(stderr, "error: png_create_info_struct returned 0.\n");
png_destroy_read_struct(&png_ptr, (png_infopp)NULL, (png_infopp)NULL);
fclose(fp);
return 0;
}
// create png info struct
png_infop end_info = png_create_info_struct(png_ptr);
if (!end_info)
{
fprintf(stderr, "error: png_create_info_struct returned 0.\n");
png_destroy_read_struct(&png_ptr, &info_ptr, (png_infopp) NULL);
fclose(fp);
return 0;
}
// the code in this if statement gets called if libpng encounters an error
if (setjmp(png_jmpbuf(png_ptr))) {
fprintf(stderr, "error from libpng\n");
png_destroy_read_struct(&png_ptr, &info_ptr, &end_info);
fclose(fp);
return 0;
}
// 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 temp_width, temp_height;
// get info about png
png_get_IHDR(png_ptr, info_ptr, &temp_width, &temp_height, &bit_depth, &color_type,
NULL, NULL, NULL);
if (width){ *width = temp_width; }
if (height){ *height = temp_height; }
// 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);
// glTexImage2d requires rows to be 4-byte aligned
rowbytes += 3 - ((rowbytes-1) % 4);
// Allocate the image_data as a big block, to be given to opengl
png_byte * image_data;
image_data = malloc(rowbytes * temp_height * sizeof(png_byte)+15);
if (image_data == NULL)
{
fprintf(stderr, "error: could not allocate memory for PNG image data\n");
png_destroy_read_struct(&png_ptr, &info_ptr, &end_info);
fclose(fp);
return 0;
}
// row_pointers is for pointing to image_data for reading the png with libpng
png_bytep * row_pointers = malloc(temp_height * sizeof(png_bytep));
if (row_pointers == NULL)
{
fprintf(stderr, "error: could not allocate memory for PNG row pointers\n");
png_destroy_read_struct(&png_ptr, &info_ptr, &end_info);
free(image_data);
fclose(fp);
return 0;
}
// set the individual row_pointers to point at the correct offsets of image_data
int i;
for (i = 0; i < temp_height; i++)
{
row_pointers[temp_height - 1 - i] = image_data + i * rowbytes;
}
// read the png into image_data through row_pointers
png_read_image(png_ptr, row_pointers);
// Generate the OpenGL texture object
GLuint texture;
glGenTextures(1, &texture);
glBindTexture(GL_TEXTURE_2D, texture);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, temp_width, temp_height, 0, GL_RGB, GL_UNSIGNED_BYTE, image_data);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
// clean up
png_destroy_read_struct(&png_ptr, &info_ptr, &end_info);
free(image_data);
free(row_pointers);
fclose(fp);
return texture;
}