How to Rotate Bitmaps Left
One of the Newton 2.x OS Q&As
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This document was exported on 7/23/97.
How to Rotate Bitmaps Left (3/5/96)
- Q: When I rotate a bitmap left using
MungeBitmap, it sometimes shifts the data. How can I rotate left correctly?
A: There is a bug in the Newton 2.0 OS that manifests when the row size of the unrotated bitmap is not an even byte boundary. The result can be a shift of data up to 7 pixels.
You can work around this bug most efficiently by replacing the left rotation with three calls to MungeBitmap using these operations: 'flipHorizontal, 'flipVertical, and 'rotateRight. ('rotateRight three times will work as well, but it is less efficient bacause flips are faster than rotates.)
Remember: "Three Rights (or Two Flips and a Right) Make a Left".