feat(home): Improve Continue Reading cover with 1-bit Atkinson dithering
- Add 1-bit BMP generation with Atkinson dithering for better quality thumbnails - Replace noise dithering with error diffusion for smoother gradients - Add fillPolygon() to GfxRenderer for proper bookmark ribbon shape - Change bookmark from rect+triangle carve to pentagon polygon - Fix bookmark inversion when Continue Reading card is selected - Show selection state on first render (not just after navigation) - Fix 1-bit BMP palette lookup in Bitmap::readRow() - Add drawBitmap1Bit() optimized path for 1-bit BMPs The 1-bit format eliminates gray passes on home screen for faster rendering while Atkinson dithering maintains good image quality through error diffusion.
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Eunchurn Park
@@ -383,7 +383,7 @@ bool Xtc::generateThumbBmp() const {
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return false;
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}
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// Create thumbnail BMP file - use 2-bit format like EPUB covers
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// Create thumbnail BMP file - use 1-bit format for fast home screen rendering (no gray passes)
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FsFile thumbBmp;
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if (!SdMan.openFileForWrite("XTC", getThumbBmpPath(), thumbBmp)) {
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Serial.printf("[%lu] [XTC] Failed to create thumb BMP file\n", millis());
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@@ -391,10 +391,10 @@ bool Xtc::generateThumbBmp() const {
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return false;
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}
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// Write 2-bit BMP header (same format as JpegToBmpConverter)
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const uint32_t rowSize = (thumbWidth * 2 + 31) / 32 * 4; // 2 bits per pixel, aligned
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// Write 1-bit BMP header for fast home screen rendering
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const uint32_t rowSize = (thumbWidth + 31) / 32 * 4; // 1 bit per pixel, aligned to 4 bytes
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const uint32_t imageSize = rowSize * thumbHeight;
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const uint32_t fileSize = 14 + 40 + 16 + imageSize; // 16 bytes for 4-color palette
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const uint32_t fileSize = 14 + 40 + 8 + imageSize; // 8 bytes for 2-color palette
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// File header
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thumbBmp.write('B');
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@@ -402,7 +402,7 @@ bool Xtc::generateThumbBmp() const {
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thumbBmp.write(reinterpret_cast<const uint8_t*>(&fileSize), 4);
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uint32_t reserved = 0;
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thumbBmp.write(reinterpret_cast<const uint8_t*>(&reserved), 4);
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uint32_t dataOffset = 14 + 40 + 16; // 2-bit palette has 4 colors (16 bytes)
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uint32_t dataOffset = 14 + 40 + 8; // 1-bit palette has 2 colors (8 bytes)
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thumbBmp.write(reinterpret_cast<const uint8_t*>(&dataOffset), 4);
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// DIB header
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@@ -414,7 +414,7 @@ bool Xtc::generateThumbBmp() const {
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thumbBmp.write(reinterpret_cast<const uint8_t*>(&heightVal), 4);
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uint16_t planes = 1;
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thumbBmp.write(reinterpret_cast<const uint8_t*>(&planes), 2);
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uint16_t bitsPerPixel = 2; // 2-bit for 4 grayscale levels
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uint16_t bitsPerPixel = 1; // 1-bit for black and white
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thumbBmp.write(reinterpret_cast<const uint8_t*>(&bitsPerPixel), 2);
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uint32_t compression = 0;
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thumbBmp.write(reinterpret_cast<const uint8_t*>(&compression), 4);
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@@ -423,22 +423,19 @@ bool Xtc::generateThumbBmp() const {
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thumbBmp.write(reinterpret_cast<const uint8_t*>(&ppmX), 4);
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int32_t ppmY = 2835;
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thumbBmp.write(reinterpret_cast<const uint8_t*>(&ppmY), 4);
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uint32_t colorsUsed = 4;
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uint32_t colorsUsed = 2;
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thumbBmp.write(reinterpret_cast<const uint8_t*>(&colorsUsed), 4);
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uint32_t colorsImportant = 4;
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uint32_t colorsImportant = 2;
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thumbBmp.write(reinterpret_cast<const uint8_t*>(&colorsImportant), 4);
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// Color palette (4 colors for 2-bit, same as JpegToBmpConverter)
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uint8_t palette[16] = {
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// Color palette (2 colors for 1-bit: black and white)
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uint8_t palette[8] = {
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0x00, 0x00, 0x00, 0x00, // Color 0: Black
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0x55, 0x55, 0x55, 0x00, // Color 1: Dark gray (85)
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0xAA, 0xAA, 0xAA, 0x00, // Color 2: Light gray (170)
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0xFF, 0xFF, 0xFF, 0x00 // Color 3: White
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0xFF, 0xFF, 0xFF, 0x00 // Color 1: White
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};
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thumbBmp.write(palette, 16);
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thumbBmp.write(palette, 8);
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// Allocate row buffer for 2-bit output
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const size_t dstRowSize = (thumbWidth * 2 + 7) / 8;
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// Allocate row buffer for 1-bit output
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uint8_t* rowBuffer = static_cast<uint8_t*>(malloc(rowSize));
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if (!rowBuffer) {
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free(pageBuffer);
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@@ -457,7 +454,7 @@ bool Xtc::generateThumbBmp() const {
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const size_t srcRowBytes = (bitDepth == 1) ? ((pageInfo.width + 7) / 8) : 0;
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for (uint16_t dstY = 0; dstY < thumbHeight; dstY++) {
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memset(rowBuffer, 0xFF, rowSize); // Start with all white (color 3)
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memset(rowBuffer, 0xFF, rowSize); // Start with all white (bit 1)
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// Calculate source Y range with bounds checking
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uint32_t srcYStart = (static_cast<uint32_t>(dstY) * scaleInv_fp) >> 16;
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@@ -519,28 +516,28 @@ bool Xtc::generateThumbBmp() const {
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}
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}
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// Calculate average grayscale and quantize to 2-bit
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// Calculate average grayscale and quantize to 1-bit with noise dithering
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uint8_t avgGray = (totalCount > 0) ? static_cast<uint8_t>(graySum / totalCount) : 255;
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// Quantize to 4 levels (same thresholds as JpegToBmpConverter)
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uint8_t twoBit;
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if (avgGray < 43) {
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twoBit = 0; // Black
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} else if (avgGray < 128) {
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twoBit = 1; // Dark gray
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} else if (avgGray < 213) {
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twoBit = 2; // Light gray
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} else {
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twoBit = 3; // White
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}
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// Hash-based noise dithering for 1-bit output
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uint32_t hash = static_cast<uint32_t>(dstX) * 374761393u + static_cast<uint32_t>(dstY) * 668265263u;
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hash = (hash ^ (hash >> 13)) * 1274126177u;
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const int threshold = static_cast<int>(hash >> 24); // 0-255
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const int adjustedThreshold = 128 + ((threshold - 128) / 2); // Range: 64-192
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// Pack 2-bit value into row buffer (MSB first)
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const size_t byteIndex = (dstX * 2) / 8;
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const size_t bitOffset = 6 - ((dstX * 2) % 8);
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// Quantize to 1-bit: 0=black, 1=white
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uint8_t oneBit = (avgGray >= adjustedThreshold) ? 1 : 0;
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// Pack 1-bit value into row buffer (MSB first, 8 pixels per byte)
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const size_t byteIndex = dstX / 8;
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const size_t bitOffset = 7 - (dstX % 8);
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// Bounds check for row buffer access
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if (byteIndex < rowSize) {
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rowBuffer[byteIndex] &= ~(0x03 << bitOffset); // Clear bits
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rowBuffer[byteIndex] |= (twoBit << bitOffset); // Set bits
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if (oneBit) {
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rowBuffer[byteIndex] |= (1 << bitOffset); // Set bit for white
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} else {
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rowBuffer[byteIndex] &= ~(1 << bitOffset); // Clear bit for black
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}
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}
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}
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