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pygame.mask

pygame module for image masks.

pygame.mask.from_surface - Returns a Mask from the given surface. | Returns a Mask from the given surface.
pygame.mask.from_threshold - Creates a mask by thresholding Surfaces | Creates a mask by thresholding Surfaces
pygame.mask.Mask - pygame object for representing 2d bitmasks | pygame object for representing 2d bitmasks

Useful for fast pixel perfect collision detection. `A` Mask uses 1bit per pixel to store which parts collide.

New in pygame `1.8`.

pygame.mask.from_surface

Returns a Mask from the given surface.
`pygame.mask.from_surface(Surface, threshold = 127) -> Mask`

Makes the transparent parts of the Surface not set, and the opaque parts set.

The alpha of each pixel is checked to see if it is greater than the given threshold.

If the Surface is color keyed, then threshold is not used.

pygame.mask.from_threshold

Creates a mask by thresholding Surfaces
`pygame.mask.from_surface(Surface, color, threshold = (0,0,0,255), othersurface = None, palette_colors = 1) -> Mask`

This is a more featureful method of getting a Mask from a Surface. If supplied with only one Surface, all pixels within the threshold of the supplied color are set in the Mask. If given the optional othersurface, all pixels in Surface that are within the threshold of the corresponding pixel in othersurface are set in the Mask.

pygame.mask.Mask

pygame object for representing 2d bitmasks
`pygame.Mask((width, height)): return Mask`

Mask.get_size - Returns the size of the mask. | Returns the size of the mask.
Mask.get_at - Returns nonzero if the bit at (x,y) is set. | Returns nonzero if the bit at (x,y) is set.
Mask.set_at - Sets the position in the mask given by x and y. | Sets the position in the mask given by x and y.
Mask.overlap - Returns the point of intersection if the masks overlap with the given offset - or None if it does not overlap. | Returns the point of intersection if the masks overlap with the given offset - or None if it does not overlap.
Mask.overlap_area - Returns the number of overlapping 'pixels'. | Returns the number of overlapping 'pixels'.
Mask.overlap_mask - Returns a mask of the overlapping pixels | Returns a mask of the overlapping pixels
Mask.fill - Sets all bits to 1 | Sets all bits to 1
Mask.clear - Sets all bits to 0 | Sets all bits to 0
Mask.invert - Flips the bits in a Mask | Flips the bits in a Mask
Mask.scale - Resizes a mask | Resizes a mask
Mask.draw - Draws a mask onto another | Draws a mask onto another
Mask.erase - Erases a mask from another | Erases a mask from another
Mask.count - Returns the number of set pixels | Returns the number of set pixels
Mask.centroid - Returns the centroid of the pixels in a Mask | Returns the centroid of the pixels in a Mask
Mask.angle - Returns the orientation of the pixels | Returns the orientation of the pixels
Mask.outline - list of points outlining an object | list of points outlining an object
Mask.convolve - Return the convolution of self with another mask. | Return the convolution of self with another mask.
Mask.connected_component - Returns a mask of a connected region of pixels. | Returns a mask of a connected region of pixels.
Mask.connected_components - Returns a list of masks of connected regions of pixels. | Returns a list of masks of connected regions of pixels.
Mask.get_bounding_rects - Returns a list of bounding rects of regions of set pixels. | Returns a list of bounding rects of regions of set pixels.

Mask.get_size

Returns the size of the mask.
`Mask.get_size() -> width,height`

Mask.get_at

Returns nonzero if the bit at (x,y) is set.
`Mask.get_at((x,y)) -> int`

Coordinates start at (0,0) is top left - just like Surfaces.

Mask.set_at

Sets the position in the mask given by x and y.
`Mask.set_at((x,y),value)`

Mask.overlap

Returns the point of intersection if the masks overlap with the given offset - or None if it does not overlap.
`Mask.overlap(othermask, offset) -> x,y`

The overlap tests uses the following offsets (which may be negative):

       +----+----------..
       |A   | yoffset
       |  +-+----------..
       +--|B
       |xoffset
       |  |
       :  :

Mask.overlap_area

Returns the number of overlapping 'pixels'.
`Mask.overlap_area(othermask, offset) -> numpixels`

You can see how many pixels overlap with the other mask given. This can be used to see in which direction things collide, or to see how much the two masks collide. An approximate collision normal can be found by calculating the gradient of the overlap area through the finite difference.

     dx = Mask.overlap_area(othermask,(x+1,y)) - Mask.overlap_area(othermask,(x-1,y))
     dy = Mask.overlap_area(othermask,(x,y+1)) - Mask.overlap_area(othermask,(x,y-1))

Mask.overlap_mask

Returns a mask of the overlapping pixels
`Mask.overlap_mask(othermask, offset) -> Mask`

Returns a Mask the size of the original Mask containing only the overlapping pixels between Mask and othermask.

Mask.fill

Sets all bits to 1
`Mask.fill()`

Sets all bits in a Mask to 1.

Mask.clear

Sets all bits to 0
`Mask.clear()`

Sets all bits in a Mask to 0.

Mask.invert

Flips the bits in a Mask
`Mask.invert()`

Flips all of the bits in a Mask, so that the set pixels turn to unset pixels and the unset pixels turn to set pixels.

Mask.scale

Resizes a mask
`Mask.scale((x, y)) -> Mask`

Returns a new Mask of the Mask scaled to the requested size.

Mask.draw

Draws a mask onto another
`Mask.draw(othermask, offset)`

Performs a bitwise `OR`, drawing othermask onto Mask.

Mask.erase

Erases a mask from another
`Mask.erase(othermask, offset)`

Erases all pixels set in othermask from Mask.

Mask.count

Returns the number of set pixels
`Mask.count() -> pixels`

Returns the number of set pixels in the Mask.

Mask.centroid

Returns the centroid of the pixels in a Mask
`Mask.centroid() -> (x, y)`

Finds the centroid, the center of pixel mass, of a Mask. Returns a coordinate tuple for the centroid of the Mask. In the event the Mask is empty, it will return (0,0).

Mask.angle

Returns the orientation of the pixels
`Mask.angle() -> theta`

Finds the approximate orientation of the pixels in the image from -90 to 90 degrees. This works best if performed on one connected component of pixels. It will return `0.0` on an empty Mask.

Mask.outline

list of points outlining an object
`Mask.outline(every = 1) -> [(x,y), (x,y) ...]`

Returns a list of points of the outline of the first object it comes across in a Mask. For this to be useful, there should probably only be one connected component of pixels in the Mask. The every option allows you to skip pixels in the outline. For example, setting it to 10 would return a list of every 10th pixel in the outline.

Mask.convolve

Return the convolution of self with another mask.
`Mask.convolve(othermask, outputmask = None, offset = (0,0)) -> Mask`

Returns a mask with the (i-offset[0],j-offset[1]) bit set if shifting othermask so that it's lower right corner pixel is at (i,j) would cause it to overlap with self.

If an outputmask is specified, the output is drawn onto outputmask and outputmask is returned. Otherwise a mask of size `self.get_size()` + `othermask.get_size()` - (1,1) is created.

Mask.connected_component

Returns a mask of a connected region of pixels.
`Mask.connected_component((x,y) = None) -> Mask`

This uses the `SAUF` algorithm to find a connected component in the Mask. It checks 8 point connectivity. By default, it will return the largest connected component in the image. Optionally, a coordinate pair of a pixel can be specified, and the connected component containing it will be returned. In the event the pixel at that location is not set, the returned Mask will be empty. The Mask returned is the same size as the original Mask.

Mask.connected_components

Returns a list of masks of connected regions of pixels.
`Mask.connected_components(min = 0) -> [Masks]`

Returns a list of masks of connected regions of pixels. An optional minimum number of pixels per connected region can be specified to filter out noise.

Mask.get_bounding_rects

Returns a list of bounding rects of regions of set pixels.
`Mask.get_bounding_rects() -> Rects`

This gets a bounding rect of connected regions of set pixels. `A` bounding rect is one for which each of the connected pixels is inside the rect.