pygame module to transform surfaces

A Surface transform is an operation that moves or resizes the pixels. All these functions take a Surface to operate on and return a new Surface with the results.

Some of the transforms are considered destructive. These means every time they are performed they lose pixel data. Common examples of this are resizing and rotating. For this reason, it is better to re-transform the original surface than to keep transforming an image multiple times. (For example, suppose you are animating a bouncing spring which expands and contracts. If you applied the size changes incrementally to the previous images, you would lose detail. Instead, always begin with the original image and scale to the desired size.)

pygame.transform.flip(Surface, xbool, ybool) -> Surface

flip vertically and horizontally

This can flip a Surface either vertically, horizontally, or both. Flipping a Surface is non-destructive and returns a new Surface with the same dimensions.

pygame.transform.scale(Surface, (width, height), DestSurface = None) -> Surface

resize to new resolution

Resizes the Surface to a new resolution. This is a fast scale operation that does not sample the results.

An optional destination surface can be used, rather than have it create a new one. This is quicker if you want to repeatedly scale something. However the destination must be the same size as the (width, height) passed in. Also the destination surface must be the same format.

pygame.transform.rotate(Surface, angle) -> Surface

rotate an image

Unfiltered counterclockwise rotation. The angle argument represents degrees and can be any floating point value. Negative angle amounts will rotate clockwise.

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.

pygame.transform.rotozoom(Surface, angle, scale) -> Surface

filtered scale and rotation

This is a combined scale and rotation transform. The resulting Surface will be a filtered 32-bit Surface. The scale argument is a floating point value that will be multiplied by the current resolution. The angle argument is a floating point value that represents the counterclockwise degrees to rotate. A negative rotation angle will rotate clockwise.

pygame.transform.scale2x(Surface, DestSurface = None) -> Surface

specialized image doubler

This will return a new image that is double the size of the original. It uses the AdvanceMAME Scale2X algorithm which does a 'jaggie-less' scale of bitmap graphics.

This really only has an effect on simple images with solid colors. On photographic and antialiased images it will look like a regular unfiltered scale.

An optional destination surface can be used, rather than have it create a new one. This is quicker if you want to repeatedly scale something. However the destination must be twice the size of the source surface passed in. Also the destination surface must be the same format.

pygame.transform.smoothscale(Surface, (width, height), DestSurface = None) -> Surface

scale a surface to an arbitrary size smoothly

Uses one of two different algorithms for scaling each dimension of the input surface as required. For shrinkage, the output pixels are area averages of the colors they cover. For expansion, a bilinear filter is used. For the x86-64 and i686 architectures, optimized MMX routines are included and will run much faster than other machine types. The size is a 2 number sequence for (width, height). This function only works for 24-bit or 32-bit surfaces. An exception will be thrown if the input surface bit depth is less than 24.

New in pygame 1.8

pygame.transform.get_smoothscale_backend() -> String

return smoothscale filter version in use: 'GENERIC', 'MMX', or 'SSE'

Shows whether or not smoothscale is using MMX or SSE acceleration. If no acceleration is available then "GENERIC" is returned. For a x86 processor the level of acceleration to use is determined at runtime.

This function is provided for pygame testing and debugging.

pygame.transform.set_smoothscale_backend(type) -> None

set smoothscale filter version to one of: 'GENERIC', 'MMX', or 'SSE'

Sets smoothscale acceleration. Takes a string argument. A value of 'GENERIC' turns off acceleration. 'MMX' uses MMX instructions only. 'SSE' allows SSE extensions as well. A value error is raised if type is not recognized or not supported by the current processor.

This function is provided for pygame testing and debugging. If smoothscale causes an invalid instruction error then it is a pygame/SDL bug that should be reported. Use this function as a temporary fix only.

pygame.transform.chop(Surface, rect) -> Surface

gets a copy of an image with an interior area removed

Extracts a portion of an image. All vertical and horizontal pixels surrounding the given rectangle area are removed. The corner areas (diagonal to the rect) are then brought together. (The original image is not altered by this operation.)

NOTE: If you want a "crop" that returns the part of an image within a rect, you can blit with a rect to a new surface or copy a subsurface.

pygame.transform.laplacian(Surface, DestSurface = None) -> Surface

find edges in a surface

Finds the edges in a surface using the laplacian algorithm.

New in pygame 1.8

pygame.transform.average_surfaces(Surfaces, DestSurface = None, palette_colors = 1) -> Surface

find the average surface from many surfaces.

Takes a sequence of surfaces and returns a surface with average colors from each of the surfaces.

palette_colors - if true we average the colors in palette, otherwise we average the pixel values. This is useful if the surface is actually greyscale colors, and not palette colors.

Note, this function currently does not handle palette using surfaces correctly.

New in pygame 1.8 palette_colors argument new in pygame 1.9

pygame.transform.average_color(Surface, Rect = None) -> Color

finds the average color of a surface

Finds the average color of a Surface or a region of a surface specified by a Rect, and returns it as a Color.

pygame.transform.threshold(dest_surf, surf, search_color, threshold=(0,0,0,0), set_color=(0,0,0,0), set_behavior=1, search_surf=None, inverse_set=False) -> num_threshold_pixels

finds which, and how many pixels in a surface are within a threshold of a 'search_color' or a 'search_surf'.

This versatile function can be used for find colors in a 'surf' close to a 'search_color' or close to colors in a separate 'search_surf'.

It can also be used to transfer pixels into a 'dest_surf' that match or don't match.

By default it sets pixels in the 'dest_surf' where all of the pixels NOT within the threshold are changed to set_color. If inverse_set is optionally set to True, the pixels that ARE within the threshold are changed to set_color.

If the optional 'search_surf' surface is given, it is used to threshold against rather than the specified 'set_color'. That is, it will find each pixel in the 'surf' that is within the 'threshold' of the pixel at the same coordinates of the 'search_surf'.

  • dest_surf (pygame.Surface or None) -- Surface we are changing. See 'set_behavior'. Should be None if counting (set_behavior is 0).
  • surf (pygame.Surface) -- Surface we are looking at.
  • search_color (pygame.Color) -- Color we are searching for.
  • threshold (pygame.Color) -- Within this distance from search_color (or search_surf). You can use a threshold of (r,g,b,a) where the r,g,b can have different thresholds. So you could use an r threshold of 40 and a blue threshold of 2 if you like.
  • set_color (pygame.Color or None) -- Color we set in dest_surf.
  • set_behavior (int) --
    • set_behavior=1 (default). Pixels in dest_surface will be changed to 'set_color'.
    • set_behavior=0 we do not change 'dest_surf', just count. Make dest_surf=None.
    • set_behavior=2 pixels set in 'dest_surf' will be from 'surf'.
  • search_surf (pygame.Surface or None) --
    • search_surf=None (default). Search against 'search_color' instead.
    • search_surf=Surface. Look at the color in 'search_surf' rather than using 'search_color'.
  • inverse_set (bool) --
    • False, default. Pixels outside of threshold are changed.
    • True, Pixels within threshold are changed.
Return type:



The number of pixels that are within the 'threshold' in 'surf' compared to either 'search_color' or search_surf.


See the threshold tests for a full of examples: https://github.com/pygame/pygame/blob/master/test/transform_test.py

    def test_threshold_dest_surf_not_change(self):
        """ the pixels within the threshold.

        All pixels not within threshold are changed to set_color.
        So there should be none changed in this test.
        (w, h) = size = (32, 32)
        threshold = (20, 20, 20, 20)
        original_color = (25, 25, 25, 25)
        original_dest_color = (65, 65, 65, 55)
        threshold_color = (10, 10, 10, 10)
        set_color = (255, 10, 10, 10)

        surf = pygame.Surface(size, pygame.SRCALPHA, 32)
        dest_surf = pygame.Surface(size, pygame.SRCALPHA, 32)
        search_surf = pygame.Surface(size, pygame.SRCALPHA, 32)


        # set_behavior=1, set dest_surface from set_color.
        # all within threshold of third_surface, so no color is set.

        pixels_within_threshold = pygame.transform.threshold(

        # # Return, of pixels within threshold is correct
        self.assertEqual(w*h, pixels_within_threshold)

        # # Size of dest surface is correct
        dest_rect = dest_surf.get_rect()
        dest_size = dest_rect.size
        self.assertEqual(size, dest_size)

        # The color is not the change_color specified for every pixel As all
        # pixels are within threshold

        for pt in test_utils.rect_area_pts(dest_rect):
            self.assertNotEqual(dest_surf.get_at(pt), set_color)
            self.assertEqual(dest_surf.get_at(pt), original_dest_color)

New in pygame 1.8 1.9.4 fixed a lot of bugs and added keyword arguments. Test your code.

© Pygame Developpers.
Licensed under the GNU LGPL License version 2.1.