pygame.transform.pixelate

[oddbookworm]

trafficstars

Addressing #2302

TODO:

• [x] tests

[Starbuck5]

Could this effect be replicated with a smoothscale down and a scale up? It could even do that in C code, and it might be faster because those are SIMD optimized?

Initial testing is promising that it replicates the effect, I didn't test performance.

[MyreMylar]

Could this effect be replicated with a smoothscale down and a scale up? It could even do that in C code, and it might be faster because those are SIMD optimized?

Initial testing is promising that it replicates the effect, I didn't test performance.

Shouldn't even need smoothscale for this, a bit of math with pixel_size versus the smallest dimension of the original image then two calls to SDL_SoftStretch should probably do it I'd have thought? Unless smoothscale is now faster than SDL_SoftStretch after recent SIMD-ifying?

Would probably be worth a look at least to see if it is faster than this current method.

[Starbuck5]

I've converted this to a draft due to large open questions about how the implementation should work.

[oddbookworm]

I'll revive this soon, I promise

[Matiiss]

How about we implement this by way of generalizing the blur transforms by adding a stride argument to them? Then we could implement this as a blur with stride equal to the blur radius. Then we'd also have the stride argument for blurs and pixelate could be like a convenience function that simply calls one of the blur functions with stride equal to radius, though I suppose it'd be called pixel size or something.

[oddbookworm]

Here's a test script you can use btw, I'm just running it from pygame-ce's root repo so the image is readily available

import pygame

pygame.init()

win = pygame.Window()
screen = win.get_surface()

surf = pygame.image.load("examples/data/alien1.png").convert_alpha()
surf = pygame.transform.scale(surf, screen.get_size())
pixel_size = 1

running = True
while running:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            running = False
        if event.type == pygame.MOUSEWHEEL:
            pixel_size = max(1, min(pixel_size + event.y, min(*surf.get_size())))

    screen.fill("black")
    screen.blit(pygame.transform.pixelate(surf, pixel_size))
    win.flip()

[oddbookworm]

@ankith26 comments fixed

[oddbookworm]

Re-requesting @MyreMylar review because of how ancient it is lol

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📥 Commits

Reviewing files that changed from the base of the PR and between dbb504a932f174fb1ecf8b79bd5a50377954a96f and 9ee2c8c63b65c792b253cd626f4f2f9ee08174a9.

📒 Files selected for processing (2)

• buildconfig/stubs/pygame/transform.pyi (1 hunks)
• src_c/transform.c (3 hunks)

Walkthrough

Introduces a new pygame.transform API pixelate(surface, pixel_size, dest_surface=None) with a C implementation performing downscale-then-upscale. Adds corresponding documentation macro and type stub, new tests for behavior and errors, and updates build-system dependencies by adding astroid<=3.3.8.

Changes

Cohort / File(s)	Summary
Transform API & Implementation src_c/transform.c, src_c/doc/transform_doc.h, buildconfig/stubs/pygame/transform.pyi	Add pixelate() public API: C function surf_pixelate with PyMethodDef entry, doc macro DOC_TRANSFORM_PIXELATE, and stub declaration with docstring.
Tests test/transform_test.py	Add helper surfaces_have_same_pixels and test_pixelate validating identity at size=1, full block effect at large size, and error handling (ValueError, OverflowError, TypeError).
Build System pyproject.toml	Append build requirement astroid<=3.3.8 under [build-system].

Sequence Diagram(s)

sequenceDiagram
  participant User
  participant pygame.transform
  participant surf_pixelate
  participant scale_to

  User->>pygame.transform: pixelate(surface, pixel_size, dest_surface?)
  pygame.transform->>surf_pixelate: dispatch
  surf_pixelate->>surf_pixelate: validate args
  surf_pixelate->>scale_to: downscale by pixel_size
  scale_to-->>surf_pixelate: intermediate surface
  surf_pixelate->>scale_to: upscale to original size (into dest or new)
  scale_to-->>surf_pixelate: pixelated surface
  surf_pixelate-->>User: return dest or new Surface

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Poem

I hop through pixels, blocky and bright,
Shrinking, then stretching—chunky delight. 🧩
A tap of transform, a bump of a byte,
Tests nibble errors, all set right.
New build snacks added—what a sight!
Pixel-party tonight—boop! 🐇✨

✨ Finishing Touches

• [ ] 📝 Generate Docstrings

🧪 Generate unit tests

• [ ] Create PR with unit tests
• [ ] Post copyable unit tests in a comment

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