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Fix transparency in capturePage (#12561)

* Fix transparent window capture. Transparency is preserved and not converted to black pixels anymore

* Add test to make sure aplha channel exists in captured image
Nitish Sakhawalkar 7 years ago
parent
eca0436f58
commit
6fc819dae1
2 changed files with 26 additions and 0 deletions
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  1. 3 0
      atom/browser/api/atom_api_web_contents.cc
  2. 23 0
      spec/api-browser-window-spec.js

+ 3 - 0
atom/browser/api/atom_api_web_contents.cc
View File 

@@ -276,6 +276,9 @@ content::ServiceWorkerContext* GetServiceWorkerContext(
 
 void OnCapturePageDone(const base::Callback<void(const gfx::Image&)>& callback,
 
                        const SkBitmap& bitmap,
 
                        content::ReadbackResponse response) {
 
+  // Hack to enable transparency in captured image
 
+  // TODO(nitsakh) Remove hack once fixed in chromium
 
+  const_cast<SkBitmap&>(bitmap).setAlphaType(kPremul_SkAlphaType);
 
   callback.Run(gfx::Image::CreateFrom1xBitmap(bitmap));
 
 }

+ 23 - 0
spec/api-browser-window-spec.js
View File 

@@ -442,6 +442,29 @@ describe('BrowserWindow module', () => {
 
         done()
 
       })
 
     })
 
+
 
+    it('preserves transparency', (done) => {
 
+      w.close()
 
+      const width = 400
 
+      const height = 400
 
+      w = new BrowserWindow({
 
+        show: false,
 
+        width: width,
 
+        height: height,
 
+        transparent: true
 
+      })
 
+      w.loadURL('data:text/html,<html><body background-color: rgba(255,255,255,0)></body></html>')
 
+      w.once('ready-to-show', () => {
 
+        w.show()
 
+        w.capturePage((image) => {
 
+          let imgBuffer = image.toPNG()
 
+          // Check 25th byte in the PNG
 
+          // Values can be 0,2,3,4, or 6. We want 6, which is RGB + Alpha
 
+          assert.equal(imgBuffer[25], 6)
 
+          done()
 
+        })
 
+      })
 
+    })
 
   })
 
 
   describe('BrowserWindow.setSize(width, height)', () => {