我正在尝试使用C读取PNG文件以与OpenCL一起使用. OpenCL不支持24位RGB图像,因此我需要将数据从RGB扩展到RGBA.我使用的PNG都是24位的,因此可以避免头痛.
我试图使用png_set_filler和png_set_add_alpha,我认为它们大致完全相同以解决问题,但它们都会导致此错误:
libpng error: sequential row overflow
这是完整的功能:
int LoadpnG24(unsigned char ** pixelBuffer,const char *filename,unsigned int *width,unsigned int *height) { png_byte header[8]; //open file as binary FILE *fp = fopen(filename,"rb"); if (!fp) { return TEXTURE_LOAD_ERROR; } //read the header fread(header,1,8,fp); //test if png int is_png = !png_sig_cmp(header,8); if (!is_png) { fclose(fp); return TEXTURE_LOAD_ERROR; } //create png struct png_structp png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING,NULL,NULL); if (!png_ptr) { fclose(fp); return (TEXTURE_LOAD_ERROR); } //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); return (TEXTURE_LOAD_ERROR); } //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); return (TEXTURE_LOAD_ERROR); } //png error stuff,not sure libpng man suggests this. if (setjmp(png_jmpbuf(png_ptr))) { png_destroy_read_struct(&png_ptr,&end_info); fclose(fp); return (TEXTURE_LOAD_ERROR); } //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); // Update the png info struct. png_read_update_info(png_ptr,info_ptr); // Row size in bytes. //png_size_t rowbytes = png_get_rowbytes(png_ptr,info_ptr); png_size_t rowbytes = sizeof(png_byte) * 4 * twidth; // Allocate the image_data as a big block,to be given to opencl png_byte *image_data = (png_byte *)malloc(sizeof(png_byte) * 4 * twidth * theight); if (!image_data) { //clean up memory and close stuff png_destroy_read_struct(&png_ptr,&end_info); fclose(fp); return TEXTURE_LOAD_ERROR; } //row_pointers is for pointing to image_data for reading the png with libpng png_bytep *row_pointers = (png_bytep *)malloc(sizeof(png_bytep) * theight); if (!row_pointers) { //clean up memory and close stuff png_destroy_read_struct(&png_ptr,&end_info); free(image_data); fclose(fp); return TEXTURE_LOAD_ERROR; } // set the individual row_pointers to point at the correct offsets of image_data for (int i = 0; i < theight; ++i) { row_pointers[i] = image_data + (i * rowbytes); } // PNG Transforms if (color_type == PNG_COLOR_TYPE_RGB) { //png_set_filler(png_ptr,0xff,PNG_FILLER_AFTER); png_set_add_alpha(png_ptr,PNG_FILLER_AFTER); } //read the png into image_data through row_pointers png_read_image(png_ptr,row_pointers); //clean up memory and close stuff png_destroy_read_struct(&png_ptr,&end_info); free(row_pointers); fclose(fp); //update width and height based on png info (*pixelBuffer) = image_data; if (width) {*width = twidth;} if (height) {*height = theight;} return TEXTURE_LOAD_OK; }
谢谢.