use libpng, ... now we just have to make it faster

Signed-off-by: Mattias Andrée <maandree@member.fsf.org>

1 files changed, 130 insertions, 0 deletions

diff --git a/src/png.c b/src/png.c
new file mode 100644
index 0000000..0944f18
--- /dev/null
+++ b/src/png.c
@@ -0,0 +1,130 @@
+/**
+ * scrotty — Screenshot program for Linux's TTY
+ * 
+ * Copyright © 2014, 2015  Mattias Andrée (maandree@member.fsf.org)
+ * 
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ * 
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#include "common.h"
+#include "png.h"
+
+#ifdef __GNUC__
+# pragma GCC diagnostic ignored "-Wpadded"
+#endif
+#include <png.h>
+
+
+/*
+ * Rationale:
+ * 
+ *   Users want their files in PNG (most often), not PNM.
+ *   Calling an external program for conversion poses
+ *   potential security risks, and is slower.
+ */
+
+
+/**
+ * Convert an image from PNM to PNG.
+ * 
+ * This is a very limited conversion implementation.
+ * It is not generally reusable. It makes assumptions
+ * that are true only necessarily for this program.
+ * 
+ * @param   fdin   The file descriptor for the image to convert (PNM).
+ * @param   fdout  The file descriptor for the output image (PNG).
+ * @return         Zero on success, -1 on error.
+ */
+int
+convert (int fdin, int fdout)
+{
+#define SCAN(...)  do { if (fscanf(in, __VA_ARGS__) != 1)  goto fail; } while (0)
+
+  FILE *in = NULL;
+  FILE *out = NULL;
+  long height, width, width3;
+  long y, x, r, g, b;
+  png_byte   *pixbuf = 0;
+  png_struct *pngbuf = NULL;
+  png_info   *pnginfo = NULL;
+  int saved_errno = 0, rc, c;
+  
+  /* Get a FILE * for the input, we want to use fscanf, there is no dscanf. */
+  in = fdopen (fdin, "r");
+  if (in == NULL)
+    goto fail;
+  /* Get a FILE * for the output, libpng wants a FILE *, not a file descriptor. */
+  out = fdopen (fdout, "w");
+  if (out == NULL)
+    goto fail;
+  
+  /* Read head. */
+  do c = fgetc(in); while ((c != '\n') && (c != EOF));
+  SCAN ("%li ", &width);
+  SCAN ("%li\n", &height);
+  do c = fgetc(in); while ((c != '\n') && (c != EOF));
+  
+  /* Allocte structures for the PNG. */
+  width3 = width * 3;
+  pixbuf = malloc ((size_t)width3 * sizeof (png_byte));
+  if (pixbuf == NULL)
+    goto fail;
+  pngbuf = png_create_write_struct (png_get_libpng_ver (NULL), NULL, NULL, NULL);
+  if (pngbuf == NULL)
+    goto fail;
+  pnginfo = png_create_info_struct (pngbuf);
+  if (pnginfo == NULL)
+    goto fail;
+  
+  /* Initialise PNG write, and write head. */
+  if (setjmp (png_jmpbuf(pngbuf))) /* Failing libpng calls jump here. */
+    goto fail;
+  png_init_io (pngbuf, out);
+  png_set_IHDR (pngbuf, pnginfo, (png_uint_32)width, (png_uint_32)height,
+		8 /* bit depth */, PNG_COLOR_TYPE_RGB, PNG_INTERLACE_NONE,
+		PNG_COMPRESSION_TYPE_BASE, PNG_FILTER_TYPE_BASE);
+  png_write_info (pngbuf, pnginfo);
+  
+  /* Read and convert body. */
+  for (y = 0; y < height; y++)
+    {
+      for (x = 0; x < width3; x += 3)
+	{
+	  SCAN ("%li\n", &r);
+	  SCAN ("%li\n", &g);
+	  SCAN ("%li\n", &b);
+	  pixbuf[x + 0] = (png_byte)r;
+	  pixbuf[x + 1] = (png_byte)g;
+	  pixbuf[x + 2] = (png_byte)b;
+	}
+      png_write_row (pngbuf, pixbuf);
+    }
+  png_write_end (pngbuf, pnginfo);
+  
+  rc = 0;
+  goto cleanup;
+ fail:
+  saved_errno = errno;
+  rc = -1;
+  goto cleanup;
+  
+ cleanup: 
+  png_destroy_write_struct (&pngbuf, (pnginfo ? &pnginfo : NULL));
+  if (in != NULL)
+    fclose (in);
+  if (out != NULL)
+    fclose (out);
+  free (pixbuf);
+  return errno = saved_errno, rc;
+}
+