+PositionImage
+merge (list<PositionImage> images)
+{
+ if (images.empty ()) {
+ return PositionImage ();
+ }
+
+ if (images.size() == 1) {
+ return images.front ();
+ }
+
+ dcpomatic::Rect<int> all (images.front().position, images.front().image->size().width, images.front().image->size().height);
+ for (list<PositionImage>::const_iterator i = images.begin(); i != images.end(); ++i) {
+ all.extend (dcpomatic::Rect<int> (i->position, i->image->size().width, i->image->size().height));
+ }
+
+ shared_ptr<Image> merged (new Image (images.front().image->pixel_format (), dcp::Size (all.width, all.height), true));
+ merged->make_transparent ();
+ for (list<PositionImage>::const_iterator i = images.begin(); i != images.end(); ++i) {
+ merged->alpha_blend (i->image, i->position - all.position());
+ }
+
+ return PositionImage (merged, all.position ());
+}
+
+string
+Image::digest () const
+{
+ MD5Digester digester;
+
+ for (int i = 0; i < components(); ++i) {
+ digester.add (data()[i], line_size()[i]);
+ }
+
+ return digester.get ();
+}
+
+bool
+operator== (Image const & a, Image const & b)
+{
+ if (a.components() != b.components() || a.pixel_format() != b.pixel_format() || a.aligned() != b.aligned()) {
+ return false;
+ }
+
+ for (int c = 0; c < a.components(); ++c) {
+ if (a.lines(c) != b.lines(c) || a.line_size()[c] != b.line_size()[c] || a.stride()[c] != b.stride()[c]) {
+ return false;
+ }
+
+ uint8_t* p = a.data()[c];
+ uint8_t* q = b.data()[c];
+ for (int y = 0; y < a.lines(c); ++y) {
+ if (memcmp (p, q, a.line_size()[c]) != 0) {
+ return false;
+ }
+
+ p += a.stride()[c];
+ q += b.stride()[c];
+ }
+ }
+
+ return true;
+}