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Use evenly-spaced dithering thresholds for factory LUT (Patryk Radtke)

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jpirnay
2026-04-06 19:19:21 +02:00
parent 4200714127
commit 398e973847
2 changed files with 30 additions and 63 deletions
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lib/GfxRenderer/BitmapHelpers.h
+26 -58
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@@ -125,37 +125,21 @@ class AtkinsonDitherer {
if (adjusted < 0) adjusted = 0;
if (adjusted > 255) adjusted = 255;
// Quantize to 4 levels
// Quantize to 4 levels — evenly-spaced midpoint thresholds for factory LUT
uint8_t quantized;
int quantizedValue;
if (false) { // original thresholds
if (adjusted < 43) {
quantized = 0;
quantizedValue = 0;
} else if (adjusted < 128) {
quantized = 1;
quantizedValue = 85;
} else if (adjusted < 213) {
quantized = 2;
quantizedValue = 170;
} else {
quantized = 3;
quantizedValue = 255;
}
} else { // fine-tuned to X4 eink display
if (adjusted < 30) {
quantized = 0;
quantizedValue = 15;
} else if (adjusted < 50) {
quantized = 1;
quantizedValue = 30;
} else if (adjusted < 140) {
quantized = 2;
quantizedValue = 80;
} else {
quantized = 3;
quantizedValue = 210;
}
if (adjusted < 43) {
quantized = 0;
quantizedValue = 0;
} else if (adjusted < 128) {
quantized = 1;
quantizedValue = 85;
} else if (adjusted < 213) {
quantized = 2;
quantizedValue = 170;
} else {
quantized = 3;
quantizedValue = 255;
}
// Calculate error (only distribute 6/8 = 75%)
@@ -229,37 +213,21 @@ class FloydSteinbergDitherer {
if (adjusted < 0) adjusted = 0;
if (adjusted > 255) adjusted = 255;
// Quantize to 4 levels (0, 85, 170, 255)
// Quantize to 4 levels — evenly-spaced midpoint thresholds for factory LUT
uint8_t quantized;
int quantizedValue;
if (false) { // original thresholds
if (adjusted < 43) {
quantized = 0;
quantizedValue = 0;
} else if (adjusted < 128) {
quantized = 1;
quantizedValue = 85;
} else if (adjusted < 213) {
quantized = 2;
quantizedValue = 170;
} else {
quantized = 3;
quantizedValue = 255;
}
} else { // fine-tuned to X4 eink display
if (adjusted < 30) {
quantized = 0;
quantizedValue = 15;
} else if (adjusted < 50) {
quantized = 1;
quantizedValue = 30;
} else if (adjusted < 140) {
quantized = 2;
quantizedValue = 80;
} else {
quantized = 3;
quantizedValue = 210;
}
if (adjusted < 43) {
quantized = 0;
quantizedValue = 0;
} else if (adjusted < 128) {
quantized = 1;
quantizedValue = 85;
} else if (adjusted < 213) {
quantized = 2;
quantizedValue = 170;
} else {
quantized = 3;
quantizedValue = 255;
}
// Calculate error