diff --git a/lib/GfxRenderer/Bitmap.cpp b/lib/GfxRenderer/Bitmap.cpp index a57eb702..577410fb 100644 --- a/lib/GfxRenderer/Bitmap.cpp +++ b/lib/GfxRenderer/Bitmap.cpp @@ -8,142 +8,9 @@ // ============================================================================ // Note: For cover images, dithering is done in JpegToBmpConverter.cpp // This file handles BMP reading - use simple quantization to avoid double-dithering -constexpr bool USE_NOISE_DITHERING = false; // Hash-based noise dithering -// Brightness/Contrast adjustments: -constexpr bool USE_BRIGHTNESS = false; // true: apply brightness/gamma adjustments -constexpr int BRIGHTNESS_BOOST = 10; // Brightness offset (0-50) -constexpr bool GAMMA_CORRECTION = false; // Gamma curve (brightens midtones) -constexpr float CONTRAST_FACTOR = 1.15f; // Contrast multiplier (1.0 = no change, >1 = more contrast) +constexpr bool USE_ATKINSON = true; // Use Atkinson dithering instead of Floyd-Steinberg // ============================================================================ -// Integer approximation of gamma correction (brightens midtones) -// Uses a simple curve: out = 255 * sqrt(in/255) ≈ sqrt(in * 255) -static inline int applyGamma(int gray) { - if (!GAMMA_CORRECTION) return gray; - // Fast integer square root approximation for gamma ~0.5 (brightening) - // This brightens dark/mid tones while preserving highlights - const int product = gray * 255; - // Newton-Raphson integer sqrt (2 iterations for good accuracy) - int x = gray; - if (x > 0) { - x = (x + product / x) >> 1; - x = (x + product / x) >> 1; - } - return x > 255 ? 255 : x; -} - -// Apply contrast adjustment around midpoint (128) -// factor > 1.0 increases contrast, < 1.0 decreases -static inline int applyContrast(int gray) { - // Integer-based contrast: (gray - 128) * factor + 128 - // Using fixed-point: factor 1.15 ≈ 115/100 - constexpr int factorNum = static_cast(CONTRAST_FACTOR * 100); - int adjusted = ((gray - 128) * factorNum) / 100 + 128; - if (adjusted < 0) adjusted = 0; - if (adjusted > 255) adjusted = 255; - return adjusted; -} -// Combined brightness/contrast/gamma adjustment -int adjustPixel(int gray) { - if (!USE_BRIGHTNESS) return gray; - - // Order: contrast first, then brightness, then gamma - gray = applyContrast(gray); - gray += BRIGHTNESS_BOOST; - if (gray > 255) gray = 255; - if (gray < 0) gray = 0; - gray = applyGamma(gray); - - return gray; -} -// Simple quantization without dithering - divide into 4 levels -// The thresholds are fine-tuned to the X4 display -uint8_t quantizeSimple(int gray) { - if (gray < 50) { - return 0; - } else if (gray < 70) { - return 1; - } else if (gray < 140) { - return 2; - } else { - return 3; - } -} - -// Hash-based noise dithering - survives downsampling without moiré artifacts -// Uses integer hash to generate pseudo-random threshold per pixel -static inline uint8_t quantizeNoise(int gray, int x, int y) { - uint32_t hash = static_cast(x) * 374761393u + static_cast(y) * 668265263u; - hash = (hash ^ (hash >> 13)) * 1274126177u; - const int threshold = static_cast(hash >> 24); - - const int scaled = gray * 3; - if (scaled < 255) { - return (scaled + threshold >= 255) ? 1 : 0; - } else if (scaled < 510) { - return ((scaled - 255) + threshold >= 255) ? 2 : 1; - } else { - return ((scaled - 510) + threshold >= 255) ? 3 : 2; - } -} - -// Main quantization function - selects between methods based on config -uint8_t quantize(int gray, int x, int y) { - if (USE_NOISE_DITHERING) { - return quantizeNoise(gray, x, y); - } else { - return quantizeSimple(gray); - } -} - -// Floyd-Steinberg quantization with error diffusion and serpentine scanning -// Returns 2-bit value (0-3) and updates error buffers -static inline uint8_t quantizeFloydSteinberg(int gray, int x, int width, int16_t* errorCurRow, int16_t* errorNextRow, - bool reverseDir) { - // Add accumulated error to this pixel - int adjusted = gray + errorCurRow[x + 1]; - // Clamp to valid range - if (adjusted < 0) adjusted = 0; - if (adjusted > 255) adjusted = 255; - - // Quantize to 4 levels (0, 85, 170, 255) - uint8_t quantized; - int quantizedValue; - 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; - } - - // Calculate error - int error = adjusted - quantizedValue; - - // Distribute error to neighbors (serpentine: direction-aware) - if (!reverseDir) { - // Left to right - errorCurRow[x + 2] += (error * 7) >> 4; // Right: 7/16 - errorNextRow[x] += (error * 3) >> 4; // Bottom-left: 3/16 - errorNextRow[x + 1] += (error * 5) >> 4; // Bottom: 5/16 - errorNextRow[x + 2] += (error) >> 4; // Bottom-right: 1/16 - } else { - // Right to left (mirrored) - errorCurRow[x] += (error * 7) >> 4; // Left: 7/16 - errorNextRow[x + 2] += (error * 3) >> 4; // Bottom-right: 3/16 - errorNextRow[x + 1] += (error * 5) >> 4; // Bottom: 5/16 - errorNextRow[x] += (error) >> 4; // Bottom-left: 1/16 - } - - return quantized; -} - Bitmap::~Bitmap() { delete[] errorCurRow; delete[] errorNextRow; @@ -270,13 +137,14 @@ BmpReaderError Bitmap::parseHeaders() { return BmpReaderError::SeekPixelDataFailed; } - // Allocate Floyd-Steinberg error buffers if enabled - if (useFloydSteinberg) { - delete[] errorCurRow; - delete[] errorNextRow; - errorCurRow = new int16_t[width + 2](); // +2 for boundary handling - errorNextRow = new int16_t[width + 2](); - prevRowY = -1; + // Create ditherer if enabled (only for 2-bit output) + // Use OUTPUT dimensions for dithering (after prescaling) + if (bpp > 2 && dithering) { + if (USE_ATKINSON) { + atkinsonDitherer = new AtkinsonDitherer(width); + } else { + fsDitherer = new FloydSteinbergDitherer(width); + } } return BmpReaderError::Ok; @@ -287,17 +155,6 @@ BmpReaderError Bitmap::readNextRow(uint8_t* data, uint8_t* rowBuffer) const { // Note: rowBuffer should be pre-allocated by the caller to size 'rowBytes' if (file.read(rowBuffer, rowBytes) != rowBytes) return BmpReaderError::ShortReadRow; - // Handle Floyd-Steinberg error buffer progression - const bool useFS = useFloydSteinberg && errorCurRow && errorNextRow; - if (useFS) { - if (prevRowY != -1) { - // Sequential access - swap buffers - int16_t* temp = errorCurRow; - errorCurRow = errorNextRow; - errorNextRow = temp; - memset(errorNextRow, 0, (width + 2) * sizeof(int16_t)); - } - } prevRowY += 1; uint8_t* outPtr = data; @@ -308,12 +165,18 @@ BmpReaderError Bitmap::readNextRow(uint8_t* data, uint8_t* rowBuffer) const { // Helper lambda to pack 2bpp color into the output stream auto packPixel = [&](const uint8_t lum) { uint8_t color; - if (useFS) { - // Floyd-Steinberg error diffusion - color = quantizeFloydSteinberg(adjustPixel(lum), currentX, width, errorCurRow, errorNextRow, false); + if (atkinsonDitherer) { + color = atkinsonDitherer->processPixel(adjustPixel(lum), currentX); + } else if (fsDitherer) { + color = fsDitherer->processPixel(adjustPixel(lum), currentX, fsDitherer->isReverseRow()); } else { - // Simple quantization or noise dithering - color = quantize(adjustPixel(lum), currentX, prevRowY); + if (bpp > 2) { + // Simple quantization or noise dithering + color = quantize(adjustPixel(lum), currentX, prevRowY); + } else { + // do not quantize 2bpp image + color = static_cast(lum >> 6); + } } currentOutByte |= (color << bitShift); if (bitShift == 0) { @@ -371,6 +234,11 @@ BmpReaderError Bitmap::readNextRow(uint8_t* data, uint8_t* rowBuffer) const { return BmpReaderError::UnsupportedBpp; } + if (atkinsonDitherer) + atkinsonDitherer->nextRow(); + else if (fsDitherer) + fsDitherer->nextRow(); + // Flush remaining bits if width is not a multiple of 4 if (bitShift != 6) *outPtr = currentOutByte; @@ -382,12 +250,9 @@ BmpReaderError Bitmap::rewindToData() const { return BmpReaderError::SeekPixelDataFailed; } - // Reset Floyd-Steinberg error buffers when rewinding - if (useFloydSteinberg && errorCurRow && errorNextRow) { - memset(errorCurRow, 0, (width + 2) * sizeof(int16_t)); - memset(errorNextRow, 0, (width + 2) * sizeof(int16_t)); - prevRowY = -1; - } + // Reset dithering when rewinding + if (fsDitherer) fsDitherer->reset(); + if (atkinsonDitherer) atkinsonDitherer->reset(); return BmpReaderError::Ok; } diff --git a/lib/GfxRenderer/Bitmap.h b/lib/GfxRenderer/Bitmap.h index 4c1bf09b..9ac7cfbb 100644 --- a/lib/GfxRenderer/Bitmap.h +++ b/lib/GfxRenderer/Bitmap.h @@ -4,6 +4,8 @@ #include +#include "BitmapHelpers.h" + enum class BmpReaderError : uint8_t { Ok = 0, FileInvalid, @@ -30,7 +32,7 @@ class Bitmap { public: static const char* errorToString(BmpReaderError err); - explicit Bitmap(FsFile& file, bool useFloydSteinberg = false) : file(file), useFloydSteinberg(useFloydSteinberg) {} + explicit Bitmap(FsFile& file, bool dithering = false) : file(file), dithering(dithering) {} ~Bitmap(); BmpReaderError parseHeaders(); BmpReaderError readNextRow(uint8_t* data, uint8_t* rowBuffer) const; @@ -46,7 +48,7 @@ class Bitmap { static uint32_t readLE32(FsFile& f); FsFile& file; - bool useFloydSteinberg = false; + bool dithering = false; int width = 0; int height = 0; bool topDown = false; @@ -59,9 +61,7 @@ class Bitmap { mutable int16_t* errorCurRow = nullptr; mutable int16_t* errorNextRow = nullptr; mutable int prevRowY = -1; // Track row progression for error propagation -}; -// Helper functions -uint8_t quantize(int gray, int x, int y); -uint8_t quantizeSimple(int gray); -int adjustPixel(int gray); + mutable AtkinsonDitherer* atkinsonDitherer = nullptr; + mutable FloydSteinbergDitherer* fsDitherer = nullptr; +}; diff --git a/lib/GfxRenderer/BitmapHelpers.cpp b/lib/GfxRenderer/BitmapHelpers.cpp new file mode 100644 index 00000000..b0d9dc06 --- /dev/null +++ b/lib/GfxRenderer/BitmapHelpers.cpp @@ -0,0 +1,90 @@ +#include "BitmapHelpers.h" + +#include + +// Brightness/Contrast adjustments: +constexpr bool USE_BRIGHTNESS = false; // true: apply brightness/gamma adjustments +constexpr int BRIGHTNESS_BOOST = 10; // Brightness offset (0-50) +constexpr bool GAMMA_CORRECTION = false; // Gamma curve (brightens midtones) +constexpr float CONTRAST_FACTOR = 1.15f; // Contrast multiplier (1.0 = no change, >1 = more contrast) +constexpr bool USE_NOISE_DITHERING = false; // Hash-based noise dithering + +// Integer approximation of gamma correction (brightens midtones) +// Uses a simple curve: out = 255 * sqrt(in/255) ≈ sqrt(in * 255) +static inline int applyGamma(int gray) { + if (!GAMMA_CORRECTION) return gray; + // Fast integer square root approximation for gamma ~0.5 (brightening) + // This brightens dark/mid tones while preserving highlights + const int product = gray * 255; + // Newton-Raphson integer sqrt (2 iterations for good accuracy) + int x = gray; + if (x > 0) { + x = (x + product / x) >> 1; + x = (x + product / x) >> 1; + } + return x > 255 ? 255 : x; +} + +// Apply contrast adjustment around midpoint (128) +// factor > 1.0 increases contrast, < 1.0 decreases +static inline int applyContrast(int gray) { + // Integer-based contrast: (gray - 128) * factor + 128 + // Using fixed-point: factor 1.15 ≈ 115/100 + constexpr int factorNum = static_cast(CONTRAST_FACTOR * 100); + int adjusted = ((gray - 128) * factorNum) / 100 + 128; + if (adjusted < 0) adjusted = 0; + if (adjusted > 255) adjusted = 255; + return adjusted; +} +// Combined brightness/contrast/gamma adjustment +int adjustPixel(int gray) { + if (!USE_BRIGHTNESS) return gray; + + // Order: contrast first, then brightness, then gamma + gray = applyContrast(gray); + gray += BRIGHTNESS_BOOST; + if (gray > 255) gray = 255; + if (gray < 0) gray = 0; + gray = applyGamma(gray); + + return gray; +} +// Simple quantization without dithering - divide into 4 levels +// The thresholds are fine-tuned to the X4 display +uint8_t quantizeSimple(int gray) { + if (gray < 45) { + return 0; + } else if (gray < 70) { + return 1; + } else if (gray < 140) { + return 2; + } else { + return 3; + } +} + +// Hash-based noise dithering - survives downsampling without moiré artifacts +// Uses integer hash to generate pseudo-random threshold per pixel +static inline uint8_t quantizeNoise(int gray, int x, int y) { + uint32_t hash = static_cast(x) * 374761393u + static_cast(y) * 668265263u; + hash = (hash ^ (hash >> 13)) * 1274126177u; + const int threshold = static_cast(hash >> 24); + + const int scaled = gray * 3; + if (scaled < 255) { + return (scaled + threshold >= 255) ? 1 : 0; + } else if (scaled < 510) { + return ((scaled - 255) + threshold >= 255) ? 2 : 1; + } else { + return ((scaled - 510) + threshold >= 255) ? 3 : 2; + } +} + +// Main quantization function - selects between methods based on config +uint8_t quantize(int gray, int x, int y) { + if (USE_NOISE_DITHERING) { + return quantizeNoise(gray, x, y); + } else { + return quantizeSimple(gray); + } +} diff --git a/lib/GfxRenderer/BitmapHelpers.h b/lib/GfxRenderer/BitmapHelpers.h new file mode 100644 index 00000000..cbacec79 --- /dev/null +++ b/lib/GfxRenderer/BitmapHelpers.h @@ -0,0 +1,222 @@ +#pragma once + +#include + +// Helper functions +uint8_t quantize(int gray, int x, int y); +uint8_t quantizeSimple(int gray); +int adjustPixel(int gray); + +// Atkinson dithering - distributes only 6/8 (75%) of error for cleaner results +// Error distribution pattern: +// X 1/8 1/8 +// 1/8 1/8 1/8 +// 1/8 +// Less error buildup = fewer artifacts than Floyd-Steinberg +class AtkinsonDitherer { + public: + AtkinsonDitherer(int width) : width(width) { + errorRow0 = new int16_t[width + 4](); // Current row + errorRow1 = new int16_t[width + 4](); // Next row + errorRow2 = new int16_t[width + 4](); // Row after next + } + + ~AtkinsonDitherer() { + delete[] errorRow0; + delete[] errorRow1; + delete[] errorRow2; + } + + uint8_t processPixel(int gray, int x) { + // Add accumulated error + int adjusted = gray + errorRow0[x + 2]; + if (adjusted < 0) adjusted = 0; + if (adjusted > 255) adjusted = 255; + + // Quantize to 4 levels + 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; + } + } + + // Calculate error (only distribute 6/8 = 75%) + int error = (adjusted - quantizedValue) >> 3; // error/8 + + // Distribute 1/8 to each of 6 neighbors + errorRow0[x + 3] += error; // Right + errorRow0[x + 4] += error; // Right+1 + errorRow1[x + 1] += error; // Bottom-left + errorRow1[x + 2] += error; // Bottom + errorRow1[x + 3] += error; // Bottom-right + errorRow2[x + 2] += error; // Two rows down + + return quantized; + } + + void nextRow() { + int16_t* temp = errorRow0; + errorRow0 = errorRow1; + errorRow1 = errorRow2; + errorRow2 = temp; + memset(errorRow2, 0, (width + 4) * sizeof(int16_t)); + } + + void reset() { + memset(errorRow0, 0, (width + 4) * sizeof(int16_t)); + memset(errorRow1, 0, (width + 4) * sizeof(int16_t)); + memset(errorRow2, 0, (width + 4) * sizeof(int16_t)); + } + + private: + int width; + int16_t* errorRow0; + int16_t* errorRow1; + int16_t* errorRow2; +}; + +// Floyd-Steinberg error diffusion dithering with serpentine scanning +// Serpentine scanning alternates direction each row to reduce "worm" artifacts +// Error distribution pattern (left-to-right): +// X 7/16 +// 3/16 5/16 1/16 +// Error distribution pattern (right-to-left, mirrored): +// 1/16 5/16 3/16 +// 7/16 X +class FloydSteinbergDitherer { + public: + FloydSteinbergDitherer(int width) : width(width), rowCount(0) { + errorCurRow = new int16_t[width + 2](); // +2 for boundary handling + errorNextRow = new int16_t[width + 2](); + } + + ~FloydSteinbergDitherer() { + delete[] errorCurRow; + delete[] errorNextRow; + } + + // Process a single pixel and return quantized 2-bit value + // x is the logical x position (0 to width-1), direction handled internally + uint8_t processPixel(int gray, int x, bool reverseDirection) { + // Add accumulated error to this pixel + int adjusted = gray + errorCurRow[x + 1]; + + // Clamp to valid range + if (adjusted < 0) adjusted = 0; + if (adjusted > 255) adjusted = 255; + + // Quantize to 4 levels (0, 85, 170, 255) + 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; + } + } + + // Calculate error + int error = adjusted - quantizedValue; + + // Distribute error to neighbors (serpentine: direction-aware) + if (!reverseDirection) { + // Left to right: standard distribution + // Right: 7/16 + errorCurRow[x + 2] += (error * 7) >> 4; + // Bottom-left: 3/16 + errorNextRow[x] += (error * 3) >> 4; + // Bottom: 5/16 + errorNextRow[x + 1] += (error * 5) >> 4; + // Bottom-right: 1/16 + errorNextRow[x + 2] += (error) >> 4; + } else { + // Right to left: mirrored distribution + // Left: 7/16 + errorCurRow[x] += (error * 7) >> 4; + // Bottom-right: 3/16 + errorNextRow[x + 2] += (error * 3) >> 4; + // Bottom: 5/16 + errorNextRow[x + 1] += (error * 5) >> 4; + // Bottom-left: 1/16 + errorNextRow[x] += (error) >> 4; + } + + return quantized; + } + + // Call at the end of each row to swap buffers + void nextRow() { + // Swap buffers + int16_t* temp = errorCurRow; + errorCurRow = errorNextRow; + errorNextRow = temp; + // Clear the next row buffer + memset(errorNextRow, 0, (width + 2) * sizeof(int16_t)); + rowCount++; + } + + // Check if current row should be processed in reverse + bool isReverseRow() const { return (rowCount & 1) != 0; } + + // Reset for a new image or MCU block + void reset() { + memset(errorCurRow, 0, (width + 2) * sizeof(int16_t)); + memset(errorNextRow, 0, (width + 2) * sizeof(int16_t)); + rowCount = 0; + } + + private: + int width; + int rowCount; + int16_t* errorCurRow; + int16_t* errorNextRow; +}; diff --git a/lib/JpegToBmpConverter/JpegToBmpConverter.cpp b/lib/JpegToBmpConverter/JpegToBmpConverter.cpp index 9613767c..f79bfa06 100644 --- a/lib/JpegToBmpConverter/JpegToBmpConverter.cpp +++ b/lib/JpegToBmpConverter/JpegToBmpConverter.cpp @@ -7,8 +7,7 @@ #include #include -#include "Bitmap.h" -#include "Dithering.h" +#include "BitmapHelpers.h" // Context structure for picojpeg callback struct JpegReadContext { @@ -356,7 +355,7 @@ bool JpegToBmpConverter::jpegFileToBmpStream(FsFile& jpegFile, Print& bmpOut) { } } else { for (int x = 0; x < outWidth; x++) { - const uint8_t gray = mcuRowBuffer[bufferY * imageInfo.m_width + x]; + const uint8_t gray = adjustPixel(mcuRowBuffer[bufferY * imageInfo.m_width + x]); uint8_t twoBit; if (atkinsonDitherer) { twoBit = atkinsonDitherer->processPixel(gray, x);