Add code to load and save pngs

Using libpng instead of the lowest-common-denominator
gdk-pixbuf loader. This will allow us to load >8bit data,
and apply gamma and color correction in the future.
For now, this still just provides RGBA8 data.

As a consequence, we are now linking against libpng.

gdk/loaders/gdkpng.c

@@ -0,0 +1,442 @@
+/* GDK - The GIMP Drawing Kit
+ * Copyright (C) 2021 Red Hat, Inc.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "config.h"
+
+#include "gdkpngprivate.h"
+
+#include "gdktexture.h"
+#include "gdktextureprivate.h"
+#include "gdkmemorytextureprivate.h"
+#include "gsk/ngl/fp16private.h"
+#include <png.h>
+#include <stdio.h>
+
+/* The main difference between the png load/save code here and
+ * gdk-pixbuf is that we can support loading 16-bit data in the
+ * future, and we can extract gamma and colorspace information
+ * to produce linear, color-corrected data.
+ */
+
+/* {{{ Callbacks */
+
+/* No sigsetjmp on Windows */
+#ifndef HAVE_SIGSETJMP
+#define sigjmp_buf jmp_buf
+#define sigsetjmp(jb, x) setjmp(jb)
+#define siglongjmp longjmp
+#endif
+
+typedef struct
+{
+  guchar *data;
+  gsize size;
+  gsize position;
+} png_io;
+
+
+static void
+png_read_func (png_structp png,
+               png_bytep   data,
+               png_size_t  size)
+{
+  png_io *io;
+
+  io = png_get_io_ptr (png);
+
+  if (io->position + size > io->size)
+    png_error (png, "Read past EOF");
+
+  memcpy (data, io->data + io->position, size);
+  io->position += size;
+}
+
+static void
+png_write_func (png_structp png,
+                png_bytep   data,
+                png_size_t  size)
+{
+  png_io *io;
+
+  io = png_get_io_ptr (png);
+
+  if (io->position > io->size ||
+      io->size - io->position  < size)
+    {
+      io->size = io->position + size;
+      io->data = g_realloc (io->data, io->size);
+    }
+
+  memcpy (io->data + io->position, data, size);
+  io->position += size;
+}
+
+static void
+png_flush_func (png_structp png)
+{
+}
+
+static png_voidp
+png_malloc_callback (png_structp o,
+                     png_size_t  size)
+{
+  return g_try_malloc (size);
+}
+
+static void
+png_free_callback (png_structp o,
+                   png_voidp   x)
+{
+  g_free (x);
+}
+
+static void
+png_simple_error_callback (png_structp     png,
+                           png_const_charp error_msg)
+{
+  GError **error = png_get_error_ptr (png);
+
+  if (error && !*error)
+    g_set_error (error,
+                 GDK_TEXTURE_ERROR, GDK_TEXTURE_ERROR_CORRUPT_IMAGE,
+                 "Error reading png (%s)", error_msg);
+
+  longjmp (png_jmpbuf (png), 1);
+}
+
+static void
+png_simple_warning_callback (png_structp     png,
+                             png_const_charp error_msg)
+{
+}
+
+/* }}} */
+/* {{{ Format conversion */
+
+static void
+unpremultiply (guchar *data,
+               int     width,
+               int     height,
+               int     stride)
+{
+  gsize x, y;
+
+  for (y = 0; y < height; y++)
+    {
+      for (x = 0; x < width; x++)
+        {
+          guchar *b = &data[x * 4];
+          guint32 pixel;
+          guchar alpha;
+
+          memcpy (&pixel, b, sizeof (guint32));
+          alpha = (pixel & 0xff000000) >> 24;
+          if (alpha == 0)
+            {
+              b[0] = 0;
+              b[1] = 0;
+              b[2] = 0;
+              b[3] = 0;
+            }
+          else
+            {
+              b[0] = (((pixel & 0x00ff0000) >> 16) * 255 + alpha / 2) / alpha;
+              b[1] = (((pixel & 0x0000ff00) >>  8) * 255 + alpha / 2) / alpha;
+              b[2] = (((pixel & 0x000000ff) >>  0) * 255 + alpha / 2) / alpha;
+              b[3] = alpha;
+            }
+        }
+      data += stride;
+    }
+}
+
+static inline int
+multiply_alpha (int alpha, int color)
+{
+  int temp = (alpha * color) + 0x80;
+  return ((temp + (temp >> 8)) >> 8);
+}
+
+static void
+premultiply_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  alpha = base[3];
+      uint32_t p;
+
+      if (alpha == 0)
+        {
+          p = 0;
+        }
+      else
+        {
+          uint8_t  red   = base[0];
+          uint8_t  green = base[1];
+          uint8_t  blue  = base[2];
+
+          if (alpha != 0xff)
+            {
+              red   = multiply_alpha (alpha, red);
+              green = multiply_alpha (alpha, green);
+              blue  = multiply_alpha (alpha, blue);
+            }
+          p = ((uint32_t)alpha << 24) | (red << 16) | (green << 8) | (blue << 0);
+        }
+      memcpy (base, &p, sizeof (uint32_t));
+  }
+}
+
+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 = (0xffu << 24) | (red << 16) | (green << 8) | (blue << 0);
+      memcpy (base, &pixel, sizeof (uint32_t));
+    }
+}
+
+/* }}} */
+/* {{{ Public API */
+
+GdkTexture *
+gdk_load_png (GBytes  *bytes,
+              GError **error)
+{
+  png_io io;
+  png_struct *png = NULL;
+  png_info *info;
+  guint width, height;
+  int depth, color_type;
+  int interlace, stride;
+  GdkMemoryFormat format;
+  guchar *buffer = NULL;
+  guchar **row_pointers = NULL;
+  GBytes *out_bytes;
+  GdkTexture *texture;
+
+  io.data = (guchar *)g_bytes_get_data (bytes, &io.size);
+  io.position = 0;
+
+  png = png_create_read_struct_2 (PNG_LIBPNG_VER_STRING,
+                                  error,
+                                  png_simple_error_callback,
+                                  png_simple_warning_callback,
+                                  NULL,
+                                  png_malloc_callback,
+                                  png_free_callback);
+  if (png == NULL)
+    {
+      g_set_error (error,
+                   GDK_TEXTURE_ERROR, GDK_TEXTURE_ERROR_INSUFFICIENT_MEMORY,
+                   "Failed to parse png image");
+      return NULL;
+    }
+
+  info = png_create_info_struct (png);
+  if (info == NULL)
+    {
+      png_destroy_read_struct (&png, NULL, NULL);
+      g_set_error (error,
+                   GDK_TEXTURE_ERROR, GDK_TEXTURE_ERROR_INSUFFICIENT_MEMORY,
+                   "Failed to parse png image");
+      return NULL;
+    }
+
+  png_set_read_fn (png, &io, png_read_func);
+
+  if (sigsetjmp (png_jmpbuf (png), 1))
+    {
+      g_free (buffer);
+      g_free (row_pointers);
+      png_destroy_read_struct (&png, &info, NULL);
+      return NULL;
+    }
+
+  png_read_info (png, info);
+
+  png_get_IHDR (png, info,
+                &width, &height, &depth,
+                &color_type, &interlace, NULL, NULL);
+
+  if (color_type == PNG_COLOR_TYPE_PALETTE)
+    png_set_palette_to_rgb (png);
+
+  if (color_type == PNG_COLOR_TYPE_GRAY)
+    png_set_expand_gray_1_2_4_to_8 (png);
+
+  if (png_get_valid (png, info, PNG_INFO_tRNS))
+    png_set_tRNS_to_alpha (png);
+
+  if (depth < 8)
+    png_set_packing (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);
+
+  png_read_update_info (png, info);
+  png_get_IHDR (png, info,
+                &width, &height, &depth,
+                &color_type, &interlace, NULL, NULL);
+  if ((depth != 8) ||
+      !(color_type == PNG_COLOR_TYPE_RGB ||
+        color_type == PNG_COLOR_TYPE_RGB_ALPHA))
+    {
+      png_destroy_read_struct (&png, &info, NULL);
+      g_set_error (error,
+                   GDK_TEXTURE_ERROR, GDK_TEXTURE_ERROR_UNSUPPORTED,
+                   "Failed to parse png image");
+      return NULL;
+    }
+
+  switch (color_type)
+    {
+    case PNG_COLOR_TYPE_RGB_ALPHA:
+      format = GDK_MEMORY_DEFAULT;
+      png_set_read_user_transform_fn (png, premultiply_data);
+      break;
+    case PNG_COLOR_TYPE_RGB:
+      format = GDK_MEMORY_DEFAULT;
+      png_set_read_user_transform_fn (png, convert_bytes_to_data);
+      break;
+    default:
+      g_assert_not_reached ();
+    }
+
+  stride = width * gdk_memory_format_bytes_per_pixel (format);
+  if (stride % 4)
+    stride += 4 - stride % 4;
+
+  buffer = g_try_malloc_n (height, stride);
+  row_pointers = g_try_malloc_n (height, sizeof (char *));
+
+  if (!buffer || !row_pointers)
+    {
+      g_free (buffer);
+      g_free (row_pointers);
+      png_destroy_read_struct (&png, &info, NULL);
+      g_set_error_literal (error,
+                           GDK_TEXTURE_ERROR, GDK_TEXTURE_ERROR_INSUFFICIENT_MEMORY,
+                           "Not enough memory to load png");
+      return NULL;
+    }
+
+  for (int i = 0; i < height; i++)
+    row_pointers[i] = &buffer[i * stride];
+
+  png_read_image (png, row_pointers);
+  png_read_end (png, info);
+
+  out_bytes = g_bytes_new_take (buffer, height * stride);
+  texture = gdk_memory_texture_new (width, height,
+                                    format,
+                                    out_bytes, stride);
+  g_bytes_unref (out_bytes);
+
+  g_free (row_pointers);
+  png_destroy_read_struct (&png, &info, NULL);
+
+  return texture;
+}
+
+GBytes *
+gdk_save_png (GdkTexture *texture)
+{
+  png_struct *png = NULL;
+  png_info *info;
+  png_io io = { NULL, 0, 0 };
+  guint width, height, stride;
+  guchar *data = NULL;
+  guchar *row;
+  int y;
+
+  width = gdk_texture_get_width (texture);
+  height = gdk_texture_get_height (texture);
+
+  stride = width * 4;
+  data = g_malloc_n (stride, height);
+  gdk_texture_download (texture, data, stride);
+  unpremultiply (data, width, height, stride);
+
+  png = png_create_write_struct_2 (PNG_LIBPNG_VER_STRING, NULL,
+                                   png_simple_error_callback,
+                                   png_simple_warning_callback,
+                                   NULL,
+                                   png_malloc_callback,
+                                   png_free_callback);
+  if (!png)
+    return NULL;
+
+  info = png_create_info_struct (png);
+  if (!info)
+    {
+      png_destroy_read_struct (&png, NULL, NULL);
+      return NULL;
+    }
+
+  if (sigsetjmp (png_jmpbuf (png), 1))
+    {
+      png_destroy_read_struct (&png, &info, NULL);
+      return NULL;
+    }
+
+  png_set_write_fn (png, &io, png_write_func, png_flush_func);
+
+  png_set_IHDR (png, info, width, height, 8,
+                PNG_COLOR_TYPE_RGB_ALPHA,
+                PNG_INTERLACE_NONE,
+                PNG_COMPRESSION_TYPE_BASE,
+                PNG_FILTER_TYPE_BASE);
+
+  png_write_info (png, info);
+  png_set_packing (png);
+
+  for (y = 0, row = data; y < height; y++, row += stride)
+    png_write_rows (png, &row, 1);
+
+  png_write_end (png, info);
+
+  png_destroy_write_struct (&png, &info);
+
+  return g_bytes_new_take (io.data, io.size);
+}
+
+/* }}} */
+
+/* vim:set foldmethod=marker expandtab: */

gdk/loaders/gdkpngprivate.h

@@ -0,0 +1,31 @@
+/* GDK - The GIMP Drawing Kit
+ * Copyright (C) 2021 Red Hat, Inc.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef __GDK_PNG_PRIVATE_H__
+#define __GDK_PNG_PRIVATE_H__
+
+#include "gdktexture.h"
+#include <gio/gio.h>
+
+#define PNG_SIGNATURE "\x89PNG"
+
+GdkTexture *gdk_load_png        (GBytes         *bytes,
+                                 GError        **error);
+
+GBytes     *gdk_save_png        (GdkTexture     *texture);
+
+#endif

gdk/meson.build

@@ -51,6 +51,7 @@ gdk_public_sources = files([
   'gdktoplevelsize.c',
   'gdktoplevel.c',
   'gdkdragsurface.c',
+  'loaders/gdkpng.c',
 ])
 
 gdk_public_headers = files([
@@ -201,6 +202,7 @@ gdk_deps = [
   platform_gio_dep,
   pangocairo_dep,
   vulkan_dep,
+  png_dep,
 ]
 
 if profiler_enabled
@@ -257,7 +259,7 @@ endif
 libgdk = static_library('gdk',
   sources: [gdk_sources, gdk_backends_gen_headers, gdkconfig],
   dependencies: gdk_deps + [libgtk_css_dep],
-  link_with: [libgtk_css, ],
+  link_with: [libgtk_css],
   include_directories: [confinc, gdkx11_inc, wlinc],
   c_args: libgdk_c_args + common_cflags,
   link_whole: gdk_backends,

meson.build

@@ -207,6 +207,17 @@ foreach func : check_functions
   endif
 endforeach
 
+# We use links() because sigsetjmp() is often a macro hidden behind other macros
+cdata.set('HAVE_SIGSETJMP',
+  cc.links('''#define _POSIX_SOURCE
+              #include <setjmp.h>
+              int main (void) {
+                sigjmp_buf env;
+                sigsetjmp (env, 0);
+                return 0;
+              }''', name: 'sigsetjmp'),
+)
+
 # Check for __uint128_t (gcc) by checking for 128-bit division
 uint128_t_src = '''int main() {
 static __uint128_t v1 = 100;
@@ -389,6 +400,10 @@ pangocairo_dep = dependency('pangocairo', version: pango_req,
 pixbuf_dep     = dependency('gdk-pixbuf-2.0', version: gdk_pixbuf_req,
                             fallback : ['gdk-pixbuf', 'gdkpixbuf_dep'],
                             default_options: ['png=enabled', 'jpeg=enabled', 'builtin_loaders=png,jpeg', 'man=false'])
+png_dep        = dependency('libpng',
+                            fallback: ['libpng', 'libpng_dep'],
+                            required: true)
+
 epoxy_dep      = dependency('epoxy', version: epoxy_req,
                             fallback: ['libepoxy', 'libepoxy_dep'])
 harfbuzz_dep   = dependency('harfbuzz', version: '>= 2.1.0', required: false,

subprojects/libpng.wrap

@@ -0,0 +1,12 @@
+[wrap-file]
+directory = libpng-1.6.37
+source_url = https://github.com/glennrp/libpng/archive/v1.6.37.tar.gz
+source_filename = libpng-1.6.37.tar.gz
+source_hash = ca74a0dace179a8422187671aee97dd3892b53e168627145271cad5b5ac81307
+patch_url = https://wrapdb.mesonbuild.com/v2/libpng_1.6.37-3/get_patch
+patch_filename = libpng-1.6.37-3-wrap.zip
+patch_hash = 6c9f32fd9150b3a96ab89be52af664e32207e10aa9f5fb9aa015989ee2dd7100
+
+[provide]
+libpng = libpng_dep
+