How to free transform image in pygame?

Question

I can't find a way to easily and efficiently transform Surfaces in pygame. By transforming I mean freely reshape an image. For example: to: I've tried converting the Surface to a numpy array and apply the operation on it, the converting it back to Surface. However, this method seems to be very slow.

No, the title does not describe the question. You have to be more specific. What transformations do you want to do? Pygame has the [`pygame.transform`](https://www.pygame.org/docs/ref/transform.html) module, [`pygame.surfarray`](https://www.pygame.org/docs/ref/surfarray.html) module and [`pygame.PixelArray`](https://www.pygame.org/docs/ref/pixelarray.html) object. A rect region of a _Surface_ can be get with [`pygame.Surface.subsurface`](https://www.pygame.org/docs/ref/surface.html#pygame.Surface.subsurface). If that doesn't suit your needs, you'll need to go through Numpy and OpenCV (cv2). — Rabbid76, Sep 21 '21 at 15:12
Possibly you are searching for [`pygame.mask.Mask`](https://www.pygame.org/docs/ref/mask.html). You can blend (clip) a _Surface_ with a _Mask_. `image.blit(mask.to_surface(), (0, 0), special_flags=pygame.BLEND_RGBA_MULT)` — Rabbid76, Sep 21 '21 at 15:14
@Rabbid76 Sorry for the ambiguity. I have clarified in the edit. — PunnyBunny, Sep 21 '21 at 23:34
The answer is simple: You cannot do this with Pygame. Pygame is just for educational purpose. However you can try to use [`pygame.surfarray.pixels3d`](https://www.pygame.org/docs/ref/surfarray.html#pygame.surfarray.pixels3d) to references the pixel of a _Surface_ directly. It would be nice to see your code. Please read [How to create a Minimal, Reproducible Example](https://stackoverflow.com/help/minimal-reproducible-example). — Rabbid76, Sep 22 '21 at 04:56

score 0 · Answer 1 · answered Sep 21 '21 at 16:27

If you just want to clip an image, you can use the pygame.maks module.

Convert a pygame.mask.Mask to a pygame.Surface with pygame.mask.Mask.to_surface. Use setsurface to specify the source image and the unsetcolor argument to specify the transparent background:

def clip_surface(surf, mask):
    return mask.to_surface(setsurface = surf.convert_alpha(), unsetcolor = (0, 0, 0, 0))

Minimal example:

import pygame

def clip_surface(surf, mask):
    return mask.to_surface(setsurface = surf.convert_alpha(), unsetcolor = (0, 0, 0, 0))

def checker_image(ts, w, h, c1, c2):
    surf = pygame.Surface((w, h))
    [pygame.draw.rect(surf, c1 if (x+y) % 2 == 0 else c2, (x*ts, y*ts, ts, ts)) for x in range((w+ts-1)//ts) for y in range((h+ts-1)//ts)]
    return surf

pygame.init()
window = pygame.display.set_mode((300, 300))
clock = pygame.time.Clock()

background = checker_image(40, *window.get_size(), (129, 128, 128), (96, 96, 96))
image = checker_image(20, 200, 200, (255, 128, 128), (255, 64, 64))
mask_image = pygame.Surface(image.get_size(), pygame.SRCALPHA)
pygame.draw.polygon(mask_image, (255, 255, 255), [(100, 10), (10, 190), (190, 190)])
mask = pygame.mask.from_surface(mask_image)

clipped_image = clip_surface(image, mask)

run = True
while run:
    clock.tick(60)
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            run = False          

    window.blit(background, (0, 0))
    image_rect = clipped_image.get_rect(center = window.get_rect().center)
    pygame.draw.rect(window, (0, 0, 0), image_rect, 3)
    window.blit(clipped_image, image_rect)
    pygame.display.flip()

pygame.quit()
exit()

How to free transform image in pygame?

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