images_-_libpng:write_a_png_to_a_file
Images - libpng - Write a PNG to a file
#include <png.h> #include <stdio.h> #include <stdlib.h> #include <stdint.h> /* Pixels in this bitmap structure are stored as BGR. */ typedef struct _RGBPixel { uint8_t blue; uint8_t green; uint8_t red; } RGBPixel; /* Structure for containing decompressed bitmaps. */ typedef struct _RGBBitmap { RGBPixel *pixels; size_t width; size_t height; size_t bytewidth; uint8_t bytes_per_pixel; } RGBBitmap; /* Returns pixel of bitmap at given point. */ #define RGBPixelAtPoint(image, x, y) \ *(((image)->pixels) + (((image)->bytewidth * (y)) \ + ((x) * (image)->bytes_per_pixel))) /* Attempts to save PNG to file; returns 0 on success, non-zero on error. */ int save_png_to_file(RGBBitmap *bitmap, const char *path) { FILE *fp = fopen(path, "wb"); png_structp png_ptr = NULL; png_infop info_ptr = NULL; size_t x, y; png_uint_32 bytes_per_row; png_byte **row_pointers = NULL; if (fp == NULL) return -1; /* Initialize the write struct. */ png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL); if (png_ptr == NULL) { fclose(fp); return -1; } /* Initialize the info struct. */ info_ptr = png_create_info_struct(png_ptr); if (info_ptr == NULL) { png_destroy_write_struct(&png_ptr, NULL); fclose(fp); return -1; } /* Set up error handling. */ if (setjmp(png_jmpbuf(png_ptr))) { png_destroy_write_struct(&png_ptr, &info_ptr); fclose(fp); return -1; } /* Set image attributes. */ png_set_IHDR(png_ptr, info_ptr, bitmap->width, bitmap->height, 8, PNG_COLOR_TYPE_RGB, PNG_INTERLACE_NONE, PNG_COMPRESSION_TYPE_DEFAULT, PNG_FILTER_TYPE_DEFAULT); /* Initialize rows of PNG. */ bytes_per_row = bitmap->width * bitmap->bytes_per_pixel; row_pointers = png_malloc(png_ptr, bitmap->height * sizeof(png_byte *)); for (y = 0; y < bitmap->height; ++y) { uint8_t *row = png_malloc(png_ptr, sizeof(uint8_t) * bitmap->bytes_per_pixel); row_pointers[y] = (png_byte *)row; for (x = 0; x < bitmap->width; ++x) { RGBPixel color = RGBPixelAtPoint(bitmap, x, y); *row++ = color.red; *row++ = color.green; *row++ = color.blue; } } /* Actually write the image data. */ png_init_io(png_ptr, fp); png_set_rows(png_ptr, info_ptr, row_pointers); png_write_png(png_ptr, info_ptr, PNG_TRANSFORM_IDENTITY, NULL); /* Cleanup. */ for (y = 0; y < bitmap->height; y++) { png_free(png_ptr, row_pointers[y]); } png_free(png_ptr, row_pointers); /* Finish writing. */ png_destroy_write_struct(&png_ptr, &info_ptr); fclose(fp); return 0; }
images_-_libpng/write_a_png_to_a_file.txt · Last modified: 2020/07/19 12:05 by 173.212.242.224