From 4e27dfb99e4188173cf7d61dd576c2ecdcc4e1d0 Mon Sep 17 00:00:00 2001
From: Malfurious <m@lfurio.us>
Date: Mon, 21 Dec 2020 02:27:32 -0500
Subject: Add libpng skeleton file

Signed-off-by: Malfurious <m@lfurio.us>
---
 automation/transform_png.c | 176 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 176 insertions(+)
 create mode 100644 automation/transform_png.c

(limited to 'automation/transform_png.c')

diff --git a/automation/transform_png.c b/automation/transform_png.c
new file mode 100644
index 0000000..f2b688e
--- /dev/null
+++ b/automation/transform_png.c
@@ -0,0 +1,176 @@
+/*
+ * Copyright 2002-2010 Guillaume Cottenceau.
+ *
+ * This software may be freely redistributed under the terms
+ * of the X11 license.
+ */
+
+#include <unistd.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <stdarg.h>
+
+#define PNG_DEBUG 3
+#include <png.h>
+
+void abort_(const char * s, ...)
+{
+    va_list args;
+    va_start(args, s);
+    vfprintf(stderr, s, args);
+    fprintf(stderr, "\n");
+    va_end(args);
+    abort();
+}
+
+int x, y;
+
+int width, height;
+png_byte color_type;
+png_byte bit_depth;
+
+png_structp png_ptr;
+png_infop info_ptr;
+int number_of_passes;
+png_bytep * row_pointers;
+
+void read_png_file(char* file_name)
+{
+    unsigned char header[8];    // 8 is the maximum size that can be checked
+
+    /* open file and test for it being a png */
+    FILE *fp = fopen(file_name, "rb");
+    if (!fp)
+        abort_("[read_png_file] File %s could not be opened for reading", file_name);
+    fread(header, 1, 8, fp);
+    if (png_sig_cmp(header, 0, 8))
+        abort_("[read_png_file] File %s is not recognized as a PNG file", file_name);
+
+    /* initialize stuff */
+    png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
+
+    if (!png_ptr)
+        abort_("[read_png_file] png_create_read_struct failed");
+
+    info_ptr = png_create_info_struct(png_ptr);
+    if (!info_ptr)
+        abort_("[read_png_file] png_create_info_struct failed");
+
+    if (setjmp(png_jmpbuf(png_ptr)))
+        abort_("[read_png_file] Error during init_io");
+
+    png_init_io(png_ptr, fp);
+    png_set_sig_bytes(png_ptr, 8);
+
+    png_read_info(png_ptr, info_ptr);
+
+    width = png_get_image_width(png_ptr, info_ptr);
+    height = png_get_image_height(png_ptr, info_ptr);
+    color_type = png_get_color_type(png_ptr, info_ptr);
+    bit_depth = png_get_bit_depth(png_ptr, info_ptr);
+
+    number_of_passes = png_set_interlace_handling(png_ptr);
+    png_read_update_info(png_ptr, info_ptr);
+
+    /* read file */
+    if (setjmp(png_jmpbuf(png_ptr)))
+        abort_("[read_png_file] Error during read_image");
+
+    row_pointers = (png_bytep*) malloc(sizeof(png_bytep) * height);
+    for (y=0; y<height; y++)
+        row_pointers[y] = (png_byte*) malloc(png_get_rowbytes(png_ptr,info_ptr));
+
+    png_read_image(png_ptr, row_pointers);
+    fclose(fp);
+}
+
+void write_png_file(char* file_name)
+{
+    /* create file */
+    FILE *fp = fopen(file_name, "wb");
+    if (!fp)
+        abort_("[write_png_file] File %s could not be opened for writing", file_name);
+
+    /* initialize stuff */
+    png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
+
+    if (!png_ptr)
+        abort_("[write_png_file] png_create_write_struct failed");
+
+    info_ptr = png_create_info_struct(png_ptr);
+    if (!info_ptr)
+        abort_("[write_png_file] png_create_info_struct failed");
+
+    if (setjmp(png_jmpbuf(png_ptr)))
+        abort_("[write_png_file] Error during init_io");
+
+    png_init_io(png_ptr, fp);
+
+    /* write header */
+    if (setjmp(png_jmpbuf(png_ptr)))
+        abort_("[write_png_file] Error during writing header");
+
+    png_set_IHDR(png_ptr, info_ptr, width, height,
+            bit_depth, color_type, PNG_INTERLACE_NONE,
+            PNG_COMPRESSION_TYPE_BASE, PNG_FILTER_TYPE_BASE);
+
+    png_write_info(png_ptr, info_ptr);
+
+    /* write bytes */
+    if (setjmp(png_jmpbuf(png_ptr)))
+        abort_("[write_png_file] Error during writing bytes");
+
+    png_write_image(png_ptr, row_pointers);
+
+    /* end write */
+    if (setjmp(png_jmpbuf(png_ptr)))
+        abort_("[write_png_file] Error during end of write");
+
+    png_write_end(png_ptr, NULL);
+
+    /* cleanup heap allocation */
+    for (y=0; y<height; y++)
+        free(row_pointers[y]);
+    free(row_pointers);
+    fclose(fp);
+}
+
+void process_file(void)
+{
+    if (png_get_color_type(png_ptr, info_ptr) == PNG_COLOR_TYPE_RGB)
+    {
+        abort_("[process_file] input file is PNG_COLOR_TYPE_RGB but must be "
+                "PNG_COLOR_TYPE_RGBA (lacks the alpha channel)");
+    }
+
+    if (png_get_color_type(png_ptr, info_ptr) != PNG_COLOR_TYPE_RGBA)
+    {
+        abort_("[process_file] color_type of input file must be "
+                "PNG_COLOR_TYPE_RGBA (%d) (is %d)",
+                PNG_COLOR_TYPE_RGBA, png_get_color_type(png_ptr, info_ptr));
+    }
+
+    for (y=0; y<height; y++)
+    {
+        png_byte* row = row_pointers[y];
+        for (x=0; x<width; x++)
+        {
+            png_byte* ptr = &(row[x*4]);
+            printf("Pixel at position [ %d - %d ] has RGBA values: %d - %d - %d - %d\n",
+                    x, y, ptr[0], ptr[1], ptr[2], ptr[3]);
+        }
+    }
+}
+
+int main(int argc, char **argv)
+{
+    if (argc != 3)
+        abort_("Usage: program_name <file_in> <file_out>");
+
+    read_png_file(argv[1]);
+    process_file();
+    write_png_file(argv[2]);
+
+    return 0;
+}
-- 
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