[cairo-png] Support generating CAIRO_FORMAT_RGB24 from PNGs.

If the PNG does not have an alpha channel, then create an opaque image.

4 files changed, 204 insertions, 17 deletions

diff --git a/src/cairo-png.c b/src/cairo-png.c
index de09086ab..bdfeda23e 100644
--- a/src/cairo-png.c
+++ b/src/cairo-png.c
@@ -33,6 +33,7 @@
  * Contributor(s):
  *	Carl D. Worth <cworth@cworth.org>
  *	Kristian Høgsberg <krh@redhat.com>
+ *	Chris Wilson <chris@chris-wilson.co.uk>
  */
 
 #include "cairoint.h"
@@ -304,7 +305,7 @@ cairo_surface_write_to_png (cairo_surface_t	*surface,
 }
 
 struct png_write_closure_t {
-    cairo_write_func_t	write_func;
+    cairo_write_func_t		 write_func;
     void			*closure;
 };
 
@@ -368,21 +369,21 @@ premultiply_data (png_structp   png,
     unsigned int i;
 
     for (i = 0; i < row_info->rowbytes; i += 4) {
-	uint8_t *base = &data[i];
+	uint8_t *base  = &data[i];
 	uint8_t  alpha = base[3];
 	uint32_t p;
 
 	if (alpha == 0) {
 	    p = 0;
 	} else {
-	    uint8_t  red = base[0];
+	    uint8_t  red   = base[0];
 	    uint8_t  green = base[1];
-	    uint8_t  blue = base[2];
+	    uint8_t  blue  = base[2];
 
 	    if (alpha != 0xff) {
-		red = multiply_alpha (alpha, red);
+		red   = multiply_alpha (alpha, red);
 		green = multiply_alpha (alpha, green);
-		blue = multiply_alpha (alpha, blue);
+		blue  = multiply_alpha (alpha, blue);
 	    }
 	    p = (alpha << 24) | (red << 16) | (green << 8) | (blue << 0);
 	}
@@ -390,6 +391,24 @@ premultiply_data (png_structp   png,
     }
 }
 
+/* Converts RGBx bytes to native endian xRGB */
+static void
+convert_bytes_to_data (png_structp png, png_row_infop row_info, png_bytep data)
+{
+    unsigned int i;
+
+    for (i = 0; i < row_info->rowbytes; i += 4) {
+	uint8_t *base  = &data[i];
+	uint8_t  red   = base[0];
+	uint8_t  green = base[1];
+	uint8_t  blue  = base[2];
+	uint32_t pixel;
+
+	pixel = (0xff << 24) | (red << 16) | (green << 8) | (blue << 0);
+	memcpy (base, &pixel, sizeof (uint32_t));
+    }
+}
+
 static cairo_surface_t *
 read_png (png_rw_ptr	read_func,
 	  void		*closure)
@@ -402,6 +421,7 @@ read_png (png_rw_ptr	read_func,
     png_uint_32 png_width, png_height;
     int depth, color_type, interlace, stride;
     unsigned int i;
+    cairo_format_t format;
     cairo_status_t status;
 
     /* XXX: Perhaps we'll want some other error handlers? */
@@ -445,7 +465,7 @@ read_png (png_rw_ptr	read_func,
         png_set_palette_to_rgb (png);
 
     /* expand gray bit depth if needed */
-    if (color_type == PNG_COLOR_TYPE_GRAY && depth < 8)
+    if (color_type == PNG_COLOR_TYPE_GRAY && (depth > 1 && depth < 8))
 #if PNG_LIBPNG_VER >= 10209
         png_set_expand_gray_1_2_4_to_8 (png);
 #else
@@ -462,20 +482,35 @@ read_png (png_rw_ptr	read_func,
         png_set_packing (png);
 
     /* convert grayscale to RGB */
-    if (color_type == PNG_COLOR_TYPE_GRAY
-        || color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
-        png_set_gray_to_rgb (png);
+    if (color_type == PNG_COLOR_TYPE_GRAY ||
+	color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
+    {
+	png_set_gray_to_rgb (png);
+    }
 
     if (interlace != PNG_INTERLACE_NONE)
         png_set_interlace_handling (png);
 
-    png_set_filler (png, 0xff, PNG_FILLER_AFTER);
+    switch (color_type) {
+	default:
+	case PNG_COLOR_TYPE_GRAY_ALPHA:
+	case PNG_COLOR_TYPE_RGB_ALPHA:
+	    format = CAIRO_FORMAT_ARGB32;
+	    png_set_read_user_transform_fn (png, premultiply_data);
+	    break;
 
-    png_set_read_user_transform_fn (png, premultiply_data);
+	case PNG_COLOR_TYPE_GRAY:
+	case PNG_COLOR_TYPE_PALETTE:
+	case PNG_COLOR_TYPE_RGB:
+	    format = CAIRO_FORMAT_RGB24;
+	    png_set_read_user_transform_fn (png, convert_bytes_to_data);
+	    png_set_filler (png, 0xff, PNG_FILLER_AFTER);
+	    break;
+    }
 
     png_read_update_info (png, info);
 
-    stride = cairo_format_stride_for_width (CAIRO_FORMAT_ARGB32, png_width);
+    stride = cairo_format_stride_for_width (format, png_width);
     if (stride < 0) {
 	surface = _cairo_surface_create_in_error (_cairo_error (CAIRO_STATUS_INVALID_STRIDE));
 	goto BAIL;
@@ -504,9 +539,9 @@ read_png (png_rw_ptr	read_func,
 	goto BAIL;
     }
 
-    surface = cairo_image_surface_create_for_data (data,
-						   CAIRO_FORMAT_ARGB32,
-						   png_width, png_height, stride);
+    surface = cairo_image_surface_create_for_data (data, format,
+						   png_width, png_height,
+						   stride);
     if (surface->status)
 	goto BAIL;
 
@@ -590,7 +625,7 @@ cairo_image_surface_create_from_png (const char *filename)
 }
 
 struct png_read_closure_t {
-    cairo_read_func_t	read_func;
+    cairo_read_func_t		 read_func;
     void			*closure;
 };
 
diff --git a/test/.gitignore b/test/.gitignore
index e56151d5b..07475218e 100644
--- a/test/.gitignore
+++ b/test/.gitignore
@@ -123,6 +123,7 @@ pdf-features
 pdf-features.pdf
 pdf-surface-source
 pdf-surface-source.pdf
+png
 png-flatten
 ps-features
 ps-features.ps
diff --git a/test/Makefile.am b/test/Makefile.am
index 30207119e..7201a98c8 100644
--- a/test/Makefile.am
+++ b/test/Makefile.am
@@ -96,6 +96,7 @@ paint-with-alpha$(EXEEXT)				\
 pattern-get-type$(EXEEXT)				\
 pattern-getters$(EXEEXT)				\
 pixman-rotate$(EXEEXT)					\
+png$(EXEEXT)						\
 push-group$(EXEEXT)					\
 radial-gradient$(EXEEXT)				\
 random-intersections$(EXEEXT)				\
@@ -623,6 +624,7 @@ fallback-resolution		\
 font-options			\
 multi-page			\
 pdf-features			\
+png				\
 ps-features			\
 svg-clip			\
 svg-surface			\
diff --git a/test/png.c b/test/png.c
new file mode 100644
index 000000000..65e465dfd
--- /dev/null
+++ b/test/png.c
@@ -0,0 +1,149 @@
+/*
+ * Copyright © 2008 Chris Wilson
+ *
+ * Permission to use, copy, modify, distribute, and sell this software
+ * and its documentation for any purpose is hereby granted without
+ * fee, provided that the above copyright notice appear in all copies
+ * and that both that copyright notice and this permission notice
+ * appear in supporting documentation, and that the name of
+ * Chris Wilson not be used in advertising or publicity pertaining to
+ * distribution of the software without specific, written prior
+ * permission. Chris Wilson makes no representations about the
+ * suitability of this software for any purpose.  It is provided "as
+ * is" without express or implied warranty.
+ *
+ * CHRIS WILSON DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS
+ * SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
+ * FITNESS, IN NO EVENT SHALL CHRIS WILSON BE LIABLE FOR ANY SPECIAL,
+ * INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER
+ * RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
+ * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR
+ * IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ *
+ * Author: Chris Wilson <chris@chris-wilson.co.uk>
+ */
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include "cairo-test.h"
+
+#include <cairo.h>
+#include <stdio.h>
+#include <stdint.h>
+#include <assert.h>
+
+/* Test the idempotency of write_png->read_png */
+
+#define RGB_MASK 0x00ffffff
+
+static cairo_bool_t
+image_surface_equals (cairo_surface_t *A, cairo_surface_t *B)
+{
+    if (cairo_image_surface_get_format (A) !=
+	cairo_image_surface_get_format (B))
+	return 0;
+
+    if (cairo_image_surface_get_width (A) !=
+	cairo_image_surface_get_width (B))
+	return 0;
+
+    if (cairo_image_surface_get_height (A) !=
+	cairo_image_surface_get_height (B))
+	return 0;
+
+    return 1;
+}
+
+static const char *
+format_to_string (cairo_format_t format)
+{
+    switch (format) {
+    case CAIRO_FORMAT_A1:     return "a1";
+    case CAIRO_FORMAT_A8:     return "a8";
+    case CAIRO_FORMAT_RGB24:  return "rgb24";
+    case CAIRO_FORMAT_ARGB32: return "argb32";
+    default: return "???";
+    }
+}
+
+static void
+print_surface (cairo_surface_t *surface)
+{
+    printf ("%s (%dx%d)\n",
+	    format_to_string (cairo_image_surface_get_format (surface)),
+	    cairo_image_surface_get_width (surface),
+	    cairo_image_surface_get_height (surface));
+}
+
+int
+main (void)
+{
+    cairo_surface_t *surface0, *surface1;
+    cairo_status_t status;
+    uint32_t argb32 = 0xdeadbede;
+
+    surface0 = cairo_image_surface_create_for_data ((unsigned char *) &argb32,
+						    CAIRO_FORMAT_ARGB32,
+						    1, 1, 4);
+    assert (cairo_surface_status (surface0) == CAIRO_STATUS_SUCCESS);
+    status = cairo_surface_write_to_png (surface0, "png-test.png");
+    if (status) {
+	printf ("Error writing 'png-test.png': %s\n",
+		cairo_status_to_string (status));
+	return CAIRO_TEST_FAILURE;
+    }
+    surface1 = cairo_image_surface_create_from_png ("png-test.png");
+    status = cairo_surface_status (surface1);
+    if (status) {
+	printf ("Error reading 'png-test.png': %s\n",
+		cairo_status_to_string (status));
+	return CAIRO_TEST_FAILURE;
+    }
+
+    if (! image_surface_equals (surface0, surface1)) {
+	printf ("Error surface mismatch.\n");
+	printf ("to png: "); print_surface (surface0);
+	printf ("from png: "); print_surface (surface1);
+	return CAIRO_TEST_FAILURE;
+    }
+    assert (*(uint32_t *) cairo_image_surface_get_data (surface1) == argb32);
+
+    cairo_surface_destroy (surface0);
+    cairo_surface_destroy (surface1);
+
+
+    surface0 = cairo_image_surface_create_for_data ((unsigned char *) &argb32,
+						    CAIRO_FORMAT_RGB24,
+						    1, 1, 4);
+    assert (cairo_surface_status (surface0) == CAIRO_STATUS_SUCCESS);
+    status = cairo_surface_write_to_png (surface0, "png-test.png");
+    if (status) {
+	printf ("Error writing 'png-test.png': %s\n",
+		cairo_status_to_string (status));
+	return CAIRO_TEST_FAILURE;
+    }
+    surface1 = cairo_image_surface_create_from_png ("png-test.png");
+    status = cairo_surface_status (surface1);
+    if (status) {
+	printf ("Error reading 'png-test.png': %s\n",
+		cairo_status_to_string (status));
+	return CAIRO_TEST_FAILURE;
+    }
+
+    if (! image_surface_equals (surface0, surface1)) {
+	printf ("Error surface mismatch.\n");
+	printf ("to png: "); print_surface (surface0);
+	printf ("from png: "); print_surface (surface1);
+	return CAIRO_TEST_FAILURE;
+    }
+    assert ((*(uint32_t *) cairo_image_surface_get_data (surface1) & RGB_MASK)
+	    == (argb32 & RGB_MASK));
+
+    cairo_surface_destroy (surface0);
+    cairo_surface_destroy (surface1);
+
+
+    return CAIRO_TEST_SUCCESS;
+}