Initial file

examples/game-of-life-png/Makefile

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+all:
+	gcc write-png.c -g -lpng
+
+clean:
+	rm -f a.out *.o *.png

examples/game-of-life-png/write-png.c

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+// Based on example program from
+// http://stackoverflow.com/q/1821806/101258
+#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)))
+//
+//#define RGBBufferAtPoint(image, x, y) \
+//    (((image)->pixels) + (((image)->bytewidth * (y)) \
+//                        + ((x) * (image)->bytes_per_pixel)))
+#define RGBPixelAtPoint(image, x, y) \
+    *(((image)->pixels) + (((image)->width * (y)) \
+                        + ((x))))
+
+#define RGBBufferAtPoint(image, x, y) \
+    (((image)->pixels) + (((image)->width * (y)) \
+                        + ((x))))
+
+/* 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) * bytes_per_row); //bitmap->bytes_per_pixel * bitmap->width);
+      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;
+}
+
+int main()
+{
+  const char path[] = "test.png";
+  int status = 0, x, y;
+  RGBBitmap img;
+  RGBPixel *pixel;
+
+  img.width = 100;
+  img.height = 100;
+  img.bytewidth = img.width; // ????
+  img.bytes_per_pixel = 3;
+  img.pixels = calloc(1, sizeof(RGBPixel) * img.width * img.height);
+
+  for (y = 0; y < img.height; y++) {
+    for (x = 0; x < img.height; x++) {
+      pixel = RGBBufferAtPoint(&img, x, y);
+      pixel->red = 255;
+      pixel->green = 255;
+      pixel->blue = 255;
+    }
+  }
+  pixel = RGBBufferAtPoint(&img, 50, 50);
+  pixel->red = 0;
+  pixel->green = 0;
+  pixel->blue = 255;
+  pixel = RGBBufferAtPoint(&img, 0, 0);
+  pixel->red = 0;
+  pixel->green = 0;
+  pixel->blue = 255;
+  pixel = RGBBufferAtPoint(&img, 99, 0);
+  pixel->red = 0;
+  pixel->green = 0;
+  pixel->blue = 255;
+  pixel = RGBBufferAtPoint(&img, 0, 99);
+  pixel->red = 0;
+  pixel->green = 0;
+  pixel->blue = 255;
+  pixel = RGBBufferAtPoint(&img, 99, 99);
+  pixel->red = 0;
+  pixel->green = 0;
+  pixel->blue = 255;
+
+  status = save_png_to_file(&img, path);
+  if (!status){
+    printf("Successfully saved %s\n", path);
+  } else {
+    printf("Unable to save %s\n", path);
+  }
+  return status;
+}