Remove (un)premultiply ops when not resizing/compositing #413

docs/changelog.md

@@ -4,6 +4,12 @@
 
 Requires libvips v8.2.3
 
+#### v0.14.2 - TBD
+
+* Remove unnecessary (un)premultiply operations when not resizing/compositing.
+  [#413](https://github.com/lovell/sharp/issues/413)
+  [@jardakotesovec](https://github.com/jardakotesovec)
+
 #### v0.14.1 - 16<sup>th</sup> April 2016
 
 * Allow removal of limitation on input pixel count via limitInputPixels. Use with care.

src/pipeline.cc

@@ -288,12 +288,12 @@ class PipelineWorker : public AsyncWorker {
       // are already less than the required dimensions
       if (baton->withoutEnlargement) {
         if (inputWidth < baton->width || inputHeight < baton->height) {
-          xfactor = 1;
-          yfactor = 1;
+          xfactor = 1.0;
+          yfactor = 1.0;
           xshrink = 1;
           yshrink = 1;
-          xresidual = 0;
-          yresidual = 0;
+          xresidual = 1.0;
+          yresidual = 1.0;
           baton->width = inputWidth;
           baton->height = inputHeight;
         }
@@ -431,7 +431,7 @@ class PipelineWorker : public AsyncWorker {
         );
       }
 
-      bool shouldAffineTransform = xresidual != 0.0 || yresidual != 0.0;
+      bool shouldAffineTransform = xresidual != 1.0 || yresidual != 1.0;
       bool shouldBlur = baton->blurSigma != 0.0;
       bool shouldSharpen = baton->sharpenRadius != 0;
       bool shouldThreshold = baton->threshold != 0;