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POAndroid: Copying a bitmap
 

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  1. POAndroid: Copying a bitmap
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    <p>A seemingly simple issue, I have an off-screen bitmap that I perform some transformations to (rotation, scaling, etc) and I'd like to store a copy of the bitmap prior to the transformations, such that in my View's <code>onDraw()</code>, I can display the transformed off-screen bitmap AND a smaller scaled version of the un-transformed bitmap as a thumbnail.</p> <p>No problem writing the off-screen bitmap in <code>onDraw()</code>, but the copied 'preserved' bitmap is also being transformed. Here is the code where I am making the copy of the bitmap, where mCanvas was created via <code>mCanvas = new Canvas(mBitmap);</code>:</p> <pre><code>mPreservedBitmap = Bitmap.createBitmap(mBitmap); // save the canvas mCanvas.save(); // do some rotations, scaling mCanvas.rotate(rotation, px, py); mCanvas.scale(scaleFactor, scaleFactor, scaleFocusX, scaleFocusY); // draw the bitmaps to the screen invalidate(); // restore the bitmap mCanvas.restore(); </code></pre> <p>In <code>onDraw()</code>, I have:</p> <pre><code>// draw the off-screen bitmap to the on-screen bitmap canvas.drawBitmap(mBitmap, 0, 0, mBitmapPaint); // draw the preserved image, scaling it to a thumbnail first canvas.drawBitmap( Bitmap.createScaledBitmap(mPreservedBitmap, (int) thumbWidth, (int) thumbHeight, true), null, thumbnailRectF, thumbCanvasPaint); </code></pre> <p>The thumbnail gets scaled to the appropriate size, but the bitmap that is being scaled down to thumbnail size is also rotated and scaled the exact same as mBitmap, which I don't want. I've also tried the Bitmap.copy() method, but with the same results. Any pointers/assitance/advice?</p> <p>Thanks,</p> <p>Paul</p>
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    1. USPaul Mennega
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    1. COIs there anything else you're doing with mCanvas from the first snippet? It doesn't seem to actually do anything (rotate etc. only affects future operations, not the image itself). And why are you trying to copy the Bitmap in onDraw? By modifying the matrix of the canvas appropriately you should be able to scale the thumbnail on the fly.
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      1. USTimo Ohr
    2. COI am using mCanvas at other points in the code to add completed shapes that the user has drawn to the off-screen bitmap. I could indeed move the createScaledBitmap code out of onDraw, I just had it in there to test out the copying/scaling.
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      1. USPaul Mennega
 

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