Pygame旋转导致图像卡死

Question

I honestly have no idea why this doesn't work. The rotate cause the image to scale up and down constantly. I looked around and haven't found a solution to my problem. Main http://tinypaste.com/1c5025fa Module http://tinypaste.com/f42f9c58

Also can someone explain why this program's box abruptly stops rotating? Etc 'http://tinypaste.com/82b3b30e' (remove the quotes, I'm not allowed to post more than 2 hyperlinks)

Answer 1

From what I can tell, the scaling that you're seeing is a sort of artifact of how the rotation operation works. As a rectangle is rotated, the bounding box will necessarily be larger than the original rectangle. See for example, the blue rectangle in the image, below. R is the radius of the rectangle...so when it's rotated, the rectangle sweeps out the area covered by the red circle in the second image. The bounding box for the rotation is the now the gray rectangle. pygame has to fill in both the red area and the gray area. What color does pygame use to fill in the padding area?

The pygame.transform.rotate docs say...

"Unless rotating by 90 degree increments, the image will be padded larger to hold the new size. If the image has pixel alphas, the padded area will be transparent. Otherwise pygame will pick a color that matches the Surface colorkey or the topleft pixel value."

So, the solution is to explicitly set the color key or alpha value for the image (in your case, when you construct your saved_image surface.) Then, when the saved_image is rotated, the newly produced image will have the padding area filled with the appropriate color.

Give it a go and see if that works.