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https://github.com/daveallie/crosspoint-reader.git
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b8e61130f2
Address review comments #2, #3, and #10: - Extract duplicated bayer4x4 matrix, applyBayerDither4Level(), and drawPixelWithRenderMode() into shared DitherUtils.h - Extract duplicated PixelCache struct into shared PixelCache.h so both JPEG and PNG decoders use the same implementation - Add MAX_CACHE_BYTES (256KB) size limit to PixelCache::allocate() to proactively guard against oversized allocations on embedded targets
41 lines
1.3 KiB
C
41 lines
1.3 KiB
C
#pragma once
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#include <GfxRenderer.h>
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#include <stdint.h>
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// 4x4 Bayer matrix for ordered dithering
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inline const uint8_t bayer4x4[4][4] = {
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{0, 8, 2, 10},
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{12, 4, 14, 6},
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{3, 11, 1, 9},
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{15, 7, 13, 5},
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};
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// Apply Bayer dithering and quantize to 4 levels (0-3)
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// Stateless - works correctly with any pixel processing order
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inline uint8_t applyBayerDither4Level(uint8_t gray, int x, int y) {
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int bayer = bayer4x4[y & 3][x & 3];
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int dither = (bayer - 8) * 5; // Scale to +/-40 (half of quantization step 85)
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int adjusted = gray + dither;
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if (adjusted < 0) adjusted = 0;
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if (adjusted > 255) adjusted = 255;
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if (adjusted < 64) return 0;
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if (adjusted < 128) return 1;
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if (adjusted < 192) return 2;
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return 3;
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}
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// Draw a pixel respecting the current render mode for grayscale support
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inline void drawPixelWithRenderMode(GfxRenderer& renderer, int x, int y, uint8_t pixelValue) {
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GfxRenderer::RenderMode renderMode = renderer.getRenderMode();
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if (renderMode == GfxRenderer::BW && pixelValue < 3) {
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renderer.drawPixel(x, y, true);
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} else if (renderMode == GfxRenderer::GRAYSCALE_MSB && (pixelValue == 1 || pixelValue == 2)) {
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renderer.drawPixel(x, y, false);
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} else if (renderMode == GfxRenderer::GRAYSCALE_LSB && pixelValue == 1) {
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renderer.drawPixel(x, y, false);
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}
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}
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