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<p class="MsoNormal"><span lang="EN-US">Hi,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">This relates to my Paint app. Doing tools to modify image, blur, invert, colorchannel swap etc. from area under your finger, like realtime brush.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Doing the bitmanipulation with javascript in canvas-onPaint works but even simple things like invert are utterly slow.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Then I decided to give ShaderEffect a try. I can successfully get image data under mouse from Canvas;<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">ShaderEffectSource {<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> sourceItem: myCanvas<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"> sourceRect: Qt.rect(x,y,w,h)<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">…<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">The shader outputs the selected part of canvas nicely on screen with fragmentShader applied. Looks great.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Now I would like to draw the shader output to my 2<sup>nd</sup> canvas, which is later drawn on top of the actual canvas if accepted by user.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">But putImageData(myShader,x,y) does not draw on canvas, and does not give any error. (other trials complain that ImageDataObject is invalid)<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">I managed to do this by calling myCanvas.grabToImage(…) and drawImage(result.url) but this is again as slow as the Javascript implementation.
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Nothing that I can use on realtime-editing. This could be used after masking an area where to apply the shader.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">If someone has any ideas?<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">-kimmo<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
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