From 55e6f6890acddfd8b415db8f92ebb7ea1a2d4166 Mon Sep 17 00:00:00 2001
From: Johny Mattsson <jmattsson@dius.com.au>
Date: Tue, 30 May 2017 17:42:34 +1000
Subject: Initial import.

---
 src/loadpng.c | 99 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 99 insertions(+)
 create mode 100644 src/loadpng.c

(limited to 'src/loadpng.c')

diff --git a/src/loadpng.c b/src/loadpng.c
new file mode 100644
index 0000000..c986ce2
--- /dev/null
+++ b/src/loadpng.c
@@ -0,0 +1,99 @@
+/*
+ * Copyright 2017 DiUS Computing Pty Ltd. All rights reserved.
+ *
+ * Released under GPLv3, see LICENSE for details.
+ *
+ * @author Johny Mattsson <jmattsson@dius.com.au>
+ */
+#include "loadpng.h"
+#include <stdlib.h>
+#include <assert.h>
+#include <png.h>
+
+static_assert(sizeof(png_byte) == sizeof( ((ql_raster_image_t *)0)->data[0]), "Code relies on png_byte being compatible with ql_raster_image_t data ");
+
+ql_raster_image_t *loadpng(const char *path)
+{
+  ql_raster_image_t *ret = NULL;
+
+  if (!path)
+    goto out;
+
+  FILE *f = fopen(path, "rb");
+  if (!f)
+    goto out;
+
+  uint8_t header[8];
+  if (fread(header, 1, sizeof(header), f) != 8)
+    goto close_out;
+
+  if (!png_check_sig(header, sizeof(header)))
+    goto close_out;
+
+  png_infop info_ptr = NULL, end_ptr = NULL;
+  png_structp png_ptr =
+    png_create_read_struct (PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
+  if (!png_ptr)
+    goto close_out;
+
+  info_ptr = png_create_info_struct(png_ptr);
+  if (!info_ptr)
+    goto destroy_read_out;
+
+  end_ptr = png_create_info_struct(png_ptr);
+  if (!end_ptr)
+    goto destroy_read_out;
+
+  if (setjmp(png_jmpbuf(png_ptr)))
+    goto destroy_read_out;
+
+  png_init_io(png_ptr, f);
+  png_set_sig_bytes(png_ptr, sizeof(header));
+
+  png_read_info(png_ptr, info_ptr);
+
+  png_set_strip_alpha(png_ptr);
+  png_set_rgb_to_gray_fixed(png_ptr, 1, -1, -1); // force into grayscale
+  png_set_expand_gray_1_2_4_to_8(png_ptr); // get us a known output format
+
+  png_read_update_info(png_ptr, info_ptr);
+
+  png_uint_32 width = png_get_image_width(png_ptr, info_ptr);
+  png_uint_32 height = png_get_image_height(png_ptr, info_ptr);
+
+  png_bytepp row_ptrs = calloc(height, sizeof(png_bytep));
+  if (!row_ptrs)
+    goto destroy_read_out;
+
+  const unsigned row_bytes = width * sizeof(png_byte);
+  ql_raster_image_t *img =
+    calloc(1, sizeof(ql_raster_image_t) + height * row_bytes);
+  if (!img)
+    goto free_image_out;
+
+  if (setjmp(png_jmpbuf(png_ptr)))
+    goto free_image_out;
+
+  for (png_uint_32 i = 0; i < height; ++i)
+    row_ptrs[i] = (png_bytep)(img->data + (i * row_bytes));
+
+  png_read_image(png_ptr, row_ptrs);
+  png_read_end(png_ptr, end_ptr);
+
+  img->height = height;
+  img->width = width;
+
+  ret = img;
+  img = NULL; // don't free it, we're returning it now
+
+free_image_out:
+  free(img);
+  free(row_ptrs);
+destroy_read_out:
+  png_destroy_read_struct(
+    &png_ptr, info_ptr ? &info_ptr : NULL, end_ptr ? &end_ptr : NULL);
+close_out:
+  fclose(f);
+out:
+  return ret;
+}
-- 
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