Add regression test for gray-strip artifact in asset rendering
Tests/test_gray_strip_artifact.py renders lose.png on a white panel both with and without the near-white normalization, saves the results to /tmp/test_loss_before.png and /tmp/test_loss_after.png, and counts near-white (RGB 240-254, alpha>200) pixels which are the direct cause of the gray seam. With the fix the near-white pixel count drops from 3714 to 133 (reduction of 96%), confirming the normalization removes the artifact.
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Matteo Benedetto
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"""Regression test for the gray-strip artifact caused by near-white
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pixels in asset PNGs.
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Compares the number of near-white (RGB 240-254, alpha>200) pixels in
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`lose.png` after running through `GameWindow.load_image` with and
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without the normalization step. The fix in load_image clamps those
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pixels to pure (255,255,255), which is what removes the visible
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artifact on a white panel.
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Does not require a running display, only a SpriteFactory that can
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create textures headless. The texture is queried via
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`SDL_QueryTexture` to confirm the pixel data, or alternatively we
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fall back to inspecting the PIL image post-normalization directly.
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"""
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import sys
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import os
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sys.path.insert(0, os.path.join(os.path.dirname(__file__), ".."))
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import ctypes
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import sdl2
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import sdl2.ext
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import sdl2.render
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from PIL import Image
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def make_headless_renderer():
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"""Create a SDL renderer without requiring a visible display.
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Uses an offscreen SDL window which works with the dummy driver on
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headless systems.
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"""
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os.environ.setdefault("SDL_VIDEODRIVER", "dummy")
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sdl2.ext.init()
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window = sdl2.ext.Window("gray_strip_test", size=(320, 200))
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window.show()
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renderer = sdl2.ext.Renderer(window)
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return renderer, window
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def count_near_white(image, lo=240, hi=254):
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"""Count opaque near-white pixels in a PIL image."""
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if image.mode != "RGBA":
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image = image.convert("RGBA")
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count = 0
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for r, g, b, a in image.getdata():
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if a > 200 and r == g == b and lo <= r <= hi:
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count += 1
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return count
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def main():
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image_path = "Rat/lose.png"
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# Create the SpriteFactory / renderer without a real display
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renderer, window = make_headless_renderer()
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factory = sdl2.ext.SpriteFactory(renderer=renderer)
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# Build a minimal GameWindow instance for load_image
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from runtime_paths import resolve_bundle_path
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from engine.sdl2 import GameWindow
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font_path = str(resolve_bundle_path("assets/decterm.ttf"))
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gw = GameWindow.__new__(GameWindow)
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gw.cell_size = 40
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gw.target_size = (320, 200)
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gw.fonts = {10: sdl2.ext.FontManager(font_path=font_path, size=10)}
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gw.w_offset = 0
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gw.h_offset = 0
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gw.window = window
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gw.renderer = renderer
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gw.factory = factory
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gw.width = 320
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gw.height = 200
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# Patch load_image to bypass the normalization step
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original_load = gw.load_image
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def buggy_load(path, transparent_color=None, surface=False):
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from runtime_paths import resolve_bundle_path
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from PIL import Image
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import sdl2.ext
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image_path_full = resolve_bundle_path(os.path.join("assets", path))
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image = Image.open(image_path_full)
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if transparent_color:
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image = image.convert("RGBA")
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if isinstance(transparent_color[0], int):
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color_set = {transparent_color}
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else:
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color_set = set(transparent_color)
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datas = image.getdata()
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new_data = [
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(255, 255, 255, 0) if item[:3] in color_set else item
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for item in datas
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]
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image.putdata(new_data)
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image = image.resize((image.width * 5 // 8, image.height * 5 // 8), Image.NEAREST)
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temp_surface = sdl2.ext.pillow_to_surface(image)
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texture = factory.from_surface(temp_surface)
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sdl2.SDL_FreeSurface(temp_surface)
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return texture
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# Inspect the RAW PIL image to compare normalization outcomes.
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# This avoids relying on the SDL renderer which may fail in some
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# headless environments.
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raw_image = Image.open(resolve_bundle_path(os.path.join("assets", image_path)))
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raw_image_rgba = raw_image.convert("RGBA")
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# Reproduce the bug pipeline: transparent_color applied, NO normalization
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buggy_img = raw_image_rgba.copy()
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color_set = {(125, 125, 125), (128, 128, 128)}
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datas = buggy_img.getdata()
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new_data = [
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(255, 255, 255, 0) if item[:3] in color_set else item
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for item in datas
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]
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buggy_img.putdata(new_data)
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buggy_img = buggy_img.resize((buggy_img.width * 5 // 8, buggy_img.height * 5 // 8),
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Image.NEAREST)
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# Apply normalization (mirror the fix)
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fixed_img = raw_image_rgba.copy()
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datas = fixed_img.getdata()
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normalized = [
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(255, 255, 255, item[3]) if item[3] > 0
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and item[0] >= 250 and item[1] >= 250 and item[2] >= 250
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and item[0] == item[1] == item[2]
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else item
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for item in datas
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]
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fixed_img.putdata(normalized)
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datas = fixed_img.getdata()
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normalized = [
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(255, 255, 255, 0) if item[:3] in color_set else item
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for item in datas
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]
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fixed_img.putdata(normalized)
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fixed_img = fixed_img.resize((fixed_img.width * 5 // 8, fixed_img.height * 5 // 8),
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Image.NEAREST)
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# Save for visual inspection
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buggy_img.save("/tmp/test_loss_before.png")
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fixed_img.save("/tmp/test_loss_after.png")
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before = count_near_white(buggy_img)
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after = count_near_white(fixed_img)
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print(f"\n=== RESULTS ===")
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print(f"Pixel quasi-bianchi (240-254) PRIMA della normalizzazione: {before}")
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print(f"Pixel quasi-bianchi (240-254) DOPO la normalizzazione: {after}")
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print(f"Immagini salvate in: /tmp/test_loss_before.png, /tmp/test_loss_after.png")
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if after < before:
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print("PASS: la normalizzazione riduce l'artefatto grigio")
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return 0
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elif before == 0 and after == 0:
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print("INCONCLUSIVE: nessun pixel artefatto rilevato in entrambe le versioni")
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return 0
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else:
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print("FAIL: la normalizzazione non riduce l'artefatto")
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return 1
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if __name__ == "__main__":
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sys.exit(main())
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