Python+GLSL Shader Deblocking Sample
This sample demonstrates how to use a simpler pixel shader to greatly reduce ASTC block artifacts, which can be quite noticeable when the block size goes beyond roughly 6x6. The shader determines if it's going to sample near an edge, and if so it samples a small vertical and horizontal region around the texel and applies a small low pass filter. The example shader is compatible with mipmapping, bilinear filtering, trilinear filtering etc. It was written to be as simple as possible.
You'll need these Python dependencies to run it:
pip install numpy Pillow glfw PyOpenGL
See run.bat for the command line on how to run the sample. Or run:
py -3.12 testbed.py shader.glsl 12 12 flower_unpacked_rgb_ASTC_LDR_12X12_RGBA_level_0_face_0_layer_0000.png flower_unpacked_rgb_ASTC_LDR_12X12_RGBA_level_1_face_0_layer_0000.png flower_unpacked_rgb_ASTC_LDR_12X12_RGBA_level_2_face_0_layer_0000.png flower_unpacked_rgb_ASTC_LDR_12X12_RGBA_level_3_face_0_layer_0000.png flower_unpacked_rgb_ASTC_LDR_12X12_RGBA_level_4_face_0_layer_0000.png
The shader can be easily simplified to sample the texture less by using less taps. The current shader uses a total of 9 taps, but 5 are possible.
Many variations and optimizations of this basic idea are possible.
Screenshots - ASTC 12x12 Block Size
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Usage and Controls
Usage: python testbed.py shader.glsl block_w block_h mip0.png mip1.png [mip2.png ...] block_w, block_h: Block size in texels (e.g. 8 8 for 8x8 DCT blocks)
Controls: Arrows Move quad left/right/up/down W / S Move closer / farther A / D Rotate yaw (cube mode) Q / E Rotate pitch (cube mode) C Toggle cube / quad mode B Bilinear filtering T Trilinear filtering P Point filtering R Reload shader 1 Toggle deblocking shader off/on 2 Toggle edge visualization (only when deblocking active) 3-4 Toggle shader const0.x/y/z/w (0 <-> 1) 5-8 Toggle shader const1.x/y/z/w (0 <-> 1) Space Reset to initial state Esc Quit
Credits
The included sunflower image is in the CC0/Public Domain, and was downloaded from here:
https://www.publicdomainpictures.net/en/view-image.php?image=756601&picture=large-yellow-sunflower
"License: CC0 Public Domain - Lynn Greyling has released this “Large Yellow Sunflower” image under Public Domain license."