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90 degree rotation of images
Question
ID
10
Category
CORIO2
Date Created
04/11/2003 11:52:52
Date Updated
04/01/2008 12:16:11
Can the CORIO2 scaler rotate images by 90 or 270 degrees?
Answer
No - this is a very difficult thing to do.

During scaling, images are stored in memory in the same way as they are input - ie. scanning each line from left to right, then moving to the next line down, etc.

Horizontal flipping is done simply by reading the memory from right to left, which is relatively easy to do. Similarly, vertical flipping is done by starting at the last line and reading backwards.

The SDRAM memory used in the scaler, like almost all other memory, is optimized for reading data within one scan line (row) at a time - and moving to the next row (scan line) takes far longer than moving to the next column (pixel). This is not normally a problem since a video screen also takes time to move to the next scan line.

However, 90 degree rotation would require moving to the next scan line (row) on every pixel, which it is not possible to do at the speed required to give a valid picture - hence 90 degree rotation is not possible on the C2 scaler.
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