test: New function to save a pixman image to .png

When debugging it is often very useful to be able to save an image as
a png file. This commit adds a function "write_png()" that does that.

If libpng is not available, then the function becomes a noop.

4 files changed, 127 insertions, 1 deletions

diff --git a/configure.ac b/configure.ac
index d06bff1..21613e1 100644
--- a/configure.ac
+++ b/configure.ac
@@ -801,6 +801,17 @@ fi
 AC_MSG_RESULT($support_for_attribute_constructor)
 AC_SUBST(TOOLCHAIN_SUPPORTS_ATTRIBUTE_CONSTRUCTOR)
 
+dnl ==================
+dnl libpng
+
+AC_CHECK_LIB([png], [png_write_info], [have_libpng=yes], [have_libpng=no])
+
+if test x$have_libpng = xyes; then
+    AC_DEFINE([HAVE_LIBPNG], [1], [Whether we have libpng])
+fi
+
+AC_SUBST(HAVE_LIBPNG)
+
 AC_OUTPUT([pixman-1.pc
            pixman-1-uninstalled.pc
            Makefile
diff --git a/test/Makefile.am b/test/Makefile.am
index 9f61fc9..52ef8ad 100644
--- a/test/Makefile.am
+++ b/test/Makefile.am
@@ -1,6 +1,6 @@
 AM_CFLAGS = @OPENMP_CFLAGS@
 AM_LDFLAGS = @OPENMP_CFLAGS@ @TESTPROGS_EXTRA_LDFLAGS@
-LDADD = $(top_builddir)/pixman/libpixman-1.la -lm
+LDADD = $(top_builddir)/pixman/libpixman-1.la -lm -lpng
 INCLUDES = -I$(top_srcdir)/pixman -I$(top_builddir)/pixman
 
 TESTPROGRAMS =			\
diff --git a/test/utils.c b/test/utils.c
index 44188ea..adabd75 100644
--- a/test/utils.c
+++ b/test/utils.c
@@ -21,6 +21,10 @@
 #include <fenv.h>
 #endif
 
+#ifdef HAVE_LIBPNG
+#include <png.h>
+#endif
+
 /* Random number seed
  */
 
@@ -335,6 +339,114 @@ make_random_bytes (int n_bytes)
     return bytes;
 }
 
+#ifdef HAVE_LIBPNG
+
+static void
+pngify_pixels (uint32_t *pixels, int n_pixels)
+{
+    int i;
+
+    for (i = 0; i < n_pixels; ++i)
+    {
+	uint32_t p = pixels[i];
+	uint8_t *out = (uint8_t *)&(pixels[i]);
+	uint8_t a, r, g, b;
+
+	a = (p & 0xff000000) >> 24;
+	r = (p & 0x00ff0000) >> 16;
+	g = (p & 0x0000ff00) >> 8;
+	b = (p & 0x000000ff) >> 0;
+
+	if (a != 0)
+	{
+	    r = (r * 255) / a;
+	    g = (g * 255) / a;
+	    b = (b * 255) / a;
+	}
+
+	*out++ = r;
+	*out++ = g;
+	*out++ = b;
+	*out++ = a;
+    }
+}
+
+pixman_bool_t
+write_png (pixman_image_t *image, const char *filename)
+{
+    int width = pixman_image_get_width (image);
+    int height = pixman_image_get_height (image);
+    int stride = width * 4;
+    uint32_t *data = malloc (height * stride);
+    pixman_image_t *copy;
+    png_struct *write_struct;
+    png_info *info_struct;
+    pixman_bool_t result = FALSE;
+    FILE *f = fopen (filename, "wb");
+    png_bytep *row_pointers;
+    int i;
+
+    if (!f)
+	return FALSE;
+
+    row_pointers = malloc (height * sizeof (png_bytep));
+
+    copy = pixman_image_create_bits (
+	PIXMAN_a8r8g8b8, width, height, data, stride);
+
+    pixman_image_composite32 (
+	PIXMAN_OP_SRC, image, NULL, copy, 0, 0, 0, 0, 0, 0, width, height);
+
+    pngify_pixels (data, height * width);
+
+    for (i = 0; i < height; ++i)
+	row_pointers[i] = (png_bytep)(data + i * width);
+
+    if (!(write_struct = png_create_write_struct (
+	      PNG_LIBPNG_VER_STRING, NULL, NULL, NULL)))
+	goto out1;
+
+    if (!(info_struct = png_create_info_struct (write_struct)))
+	goto out2;
+
+    png_init_io (write_struct, f);
+
+    png_set_IHDR (write_struct, info_struct, width, height,
+		  8, PNG_COLOR_TYPE_RGB_ALPHA,
+		  PNG_INTERLACE_NONE, PNG_COMPRESSION_TYPE_BASE,
+		  PNG_FILTER_TYPE_BASE);
+
+    png_write_info (write_struct, info_struct);
+
+    png_write_image (write_struct, row_pointers);
+
+    png_write_end (write_struct, NULL);
+
+    result = TRUE;
+
+out2:
+    png_destroy_write_struct (&write_struct, &info_struct);
+
+out1:
+    if (fclose (f) != 0)
+	result = FALSE;
+
+    pixman_image_unref (copy);
+    free (row_pointers);
+    free (data);
+    return result;
+}
+
+#else /* no libpng */
+
+pixman_bool_t
+write_png (pixman_image_t *image, const char *filename)
+{
+    return FALSE;
+}
+
+#endif
+
 /*
  * A function, which can be used as a core part of the test programs,
  * intended to detect various problems with the help of fuzzing input
diff --git a/test/utils.h b/test/utils.h
index f0c9c30..3790483 100644
--- a/test/utils.h
+++ b/test/utils.h
@@ -105,6 +105,9 @@ fail_after (int seconds, const char *msg);
 /* If possible, enable traps for floating point exceptions */
 void enable_fp_exceptions(void);
 
+pixman_bool_t
+write_png (pixman_image_t *image, const char *filename);
+
 /* A pair of macros which can help to detect corruption of
  * floating point registers after a function call. This may
  * happen if _mm_empty() call is forgotten in MMX/SSE2 fast