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.

lib/Epub/Epub.cpp

@@ -369,10 +369,11 @@ bool Epub::generateThumbBmp() const {
       return false;
     }
     // Use smaller target size for Continue Reading card (half of screen: 240x400)
+    // Generate 1-bit BMP for fast home screen rendering (no gray passes needed)
     constexpr int THUMB_TARGET_WIDTH = 240;
     constexpr int THUMB_TARGET_HEIGHT = 400;
     const bool success =
-        JpegToBmpConverter::jpegFileToBmpStreamWithSize(coverJpg, thumbBmp, THUMB_TARGET_WIDTH, THUMB_TARGET_HEIGHT);
+        JpegToBmpConverter::jpegFileTo1BitBmpStreamWithSize(coverJpg, thumbBmp, THUMB_TARGET_WIDTH, THUMB_TARGET_HEIGHT);
     coverJpg.close();
     thumbBmp.close();
     SdMan.remove(coverJpgTempPath.c_str());

lib/GfxRenderer/Bitmap.cpp

@@ -341,7 +341,10 @@ BmpReaderError Bitmap::readRow(uint8_t* data, uint8_t* rowBuffer, int rowY) cons
     }
     case 1: {
       for (int x = 0; x < width; x++) {
-        lum = (rowBuffer[x >> 3] & (0x80 >> (x & 7))) ? 0xFF : 0x00;
+        // Get palette index (0 or 1) from bit at position x
+        const uint8_t palIndex = (rowBuffer[x >> 3] & (0x80 >> (x & 7))) ? 1 : 0;
+        // Use palette lookup for proper black/white mapping
+        lum = paletteLum[palIndex];
         packPixel(lum);
       }
       break;

lib/GfxRenderer/Bitmap.h

@@ -38,6 +38,8 @@ class Bitmap {
   bool isTopDown() const { return topDown; }
   bool hasGreyscale() const { return bpp > 1; }
   int getRowBytes() const { return rowBytes; }
+  bool is1Bit() const { return bpp == 1; }
+  uint16_t getBpp() const { return bpp; }
 
  private:
   static uint16_t readLE16(FsFile& f);

lib/GfxRenderer/GfxRenderer.cpp

@@ -154,6 +154,12 @@ void GfxRenderer::drawImage(const uint8_t bitmap[], const int x, const int y, co
 
 void GfxRenderer::drawBitmap(const Bitmap& bitmap, const int x, const int y, const int maxWidth,
                              const int maxHeight) const {
+  // For 1-bit bitmaps, use optimized 1-bit rendering path
+  if (bitmap.is1Bit()) {
+    drawBitmap1Bit(bitmap, x, y, maxWidth, maxHeight);
+    return;
+  }
+
   float scale = 1.0f;
   bool isScaled = false;
   if (maxWidth > 0 && bitmap.getWidth() > maxWidth) {
@@ -222,6 +228,141 @@ void GfxRenderer::drawBitmap(const Bitmap& bitmap, const int x, const int y, con
   free(rowBytes);
 }
 
+void GfxRenderer::drawBitmap1Bit(const Bitmap& bitmap, const int x, const int y, const int maxWidth,
+                                  const int maxHeight) const {
+  float scale = 1.0f;
+  bool isScaled = false;
+  if (maxWidth > 0 && bitmap.getWidth() > maxWidth) {
+    scale = static_cast<float>(maxWidth) / static_cast<float>(bitmap.getWidth());
+    isScaled = true;
+  }
+  if (maxHeight > 0 && bitmap.getHeight() > maxHeight) {
+    scale = std::min(scale, static_cast<float>(maxHeight) / static_cast<float>(bitmap.getHeight()));
+    isScaled = true;
+  }
+
+  // For 1-bit BMP, output is still 2-bit packed (for consistency with readRow)
+  const int outputRowSize = (bitmap.getWidth() + 3) / 4;
+  auto* outputRow = static_cast<uint8_t*>(malloc(outputRowSize));
+  auto* rowBytes = static_cast<uint8_t*>(malloc(bitmap.getRowBytes()));
+
+  if (!outputRow || !rowBytes) {
+    Serial.printf("[%lu] [GFX] !! Failed to allocate 1-bit BMP row buffers\n", millis());
+    free(outputRow);
+    free(rowBytes);
+    return;
+  }
+
+  for (int bmpY = 0; bmpY < bitmap.getHeight(); bmpY++) {
+    const int bmpYOffset = bitmap.isTopDown() ? bmpY : bitmap.getHeight() - 1 - bmpY;
+    int screenY = y + (isScaled ? static_cast<int>(std::floor(bmpYOffset * scale)) : bmpYOffset);
+    if (screenY >= getScreenHeight()) {
+      break;
+    }
+    if (screenY < 0) {
+      continue;
+    }
+
+    if (bitmap.readRow(outputRow, rowBytes, bmpY) != BmpReaderError::Ok) {
+      Serial.printf("[%lu] [GFX] Failed to read row %d from 1-bit bitmap\n", millis(), bmpY);
+      free(outputRow);
+      free(rowBytes);
+      return;
+    }
+
+    for (int bmpX = 0; bmpX < bitmap.getWidth(); bmpX++) {
+      int screenX = x + (isScaled ? static_cast<int>(std::floor(bmpX * scale)) : bmpX);
+      if (screenX >= getScreenWidth()) {
+        break;
+      }
+      if (screenX < 0) {
+        continue;
+      }
+
+      // Get 2-bit value (result of readRow quantization)
+      const uint8_t val = outputRow[bmpX / 4] >> (6 - ((bmpX * 2) % 8)) & 0x3;
+
+      // For 1-bit source: 0 or 1 -> map to black (0,1,2) or white (3)
+      // val < 3 means black pixel (draw it)
+      if (val < 3) {
+        drawPixel(screenX, screenY, true);
+      }
+      // White pixels (val == 3) are not drawn (leave background)
+    }
+  }
+
+  free(outputRow);
+  free(rowBytes);
+}
+
+void GfxRenderer::fillPolygon(const int* xPoints, const int* yPoints, int numPoints, bool state) const {
+  if (numPoints < 3) return;
+
+  // Find bounding box
+  int minY = yPoints[0], maxY = yPoints[0];
+  for (int i = 1; i < numPoints; i++) {
+    if (yPoints[i] < minY) minY = yPoints[i];
+    if (yPoints[i] > maxY) maxY = yPoints[i];
+  }
+
+  // Clip to screen
+  if (minY < 0) minY = 0;
+  if (maxY >= getScreenHeight()) maxY = getScreenHeight() - 1;
+
+  // Allocate node buffer for scanline algorithm
+  auto* nodeX = static_cast<int*>(malloc(numPoints * sizeof(int)));
+  if (!nodeX) {
+    Serial.printf("[%lu] [GFX] !! Failed to allocate polygon node buffer\n", millis());
+    return;
+  }
+
+  // Scanline fill algorithm
+  for (int scanY = minY; scanY <= maxY; scanY++) {
+    int nodes = 0;
+
+    // Find all intersection points with edges
+    int j = numPoints - 1;
+    for (int i = 0; i < numPoints; i++) {
+      if ((yPoints[i] < scanY && yPoints[j] >= scanY) || (yPoints[j] < scanY && yPoints[i] >= scanY)) {
+        // Calculate X intersection using fixed-point to avoid float
+        int dy = yPoints[j] - yPoints[i];
+        if (dy != 0) {
+          nodeX[nodes++] = xPoints[i] + (scanY - yPoints[i]) * (xPoints[j] - xPoints[i]) / dy;
+        }
+      }
+      j = i;
+    }
+
+    // Sort nodes by X (simple bubble sort, numPoints is small)
+    for (int i = 0; i < nodes - 1; i++) {
+      for (int k = i + 1; k < nodes; k++) {
+        if (nodeX[i] > nodeX[k]) {
+          int temp = nodeX[i];
+          nodeX[i] = nodeX[k];
+          nodeX[k] = temp;
+        }
+      }
+    }
+
+    // Fill between pairs of nodes
+    for (int i = 0; i < nodes - 1; i += 2) {
+      int startX = nodeX[i];
+      int endX = nodeX[i + 1];
+
+      // Clip to screen
+      if (startX < 0) startX = 0;
+      if (endX >= getScreenWidth()) endX = getScreenWidth() - 1;
+
+      // Draw horizontal line
+      for (int x = startX; x <= endX; x++) {
+        drawPixel(x, scanY, state);
+      }
+    }
+  }
+
+  free(nodeX);
+}
+
 void GfxRenderer::clearScreen(const uint8_t color) const { einkDisplay.clearScreen(color); }
 
 void GfxRenderer::invertScreen() const {
@@ -436,29 +577,6 @@ void GfxRenderer::restoreBwBuffer() {
   Serial.printf("[%lu] [GFX] Restored and freed BW buffer chunks\n", millis());
 }
 
-bool GfxRenderer::copyStoredBwBuffer() {
-  // Check if all chunks are allocated
-  for (const auto& bwBufferChunk : bwBufferChunks) {
-    if (!bwBufferChunk) {
-      return false;
-    }
-  }
-
-  uint8_t* frameBuffer = einkDisplay.getFrameBuffer();
-  if (!frameBuffer) {
-    return false;
-  }
-
-  for (size_t i = 0; i < BW_BUFFER_NUM_CHUNKS; i++) {
-    const size_t offset = i * BW_BUFFER_CHUNK_SIZE;
-    memcpy(frameBuffer + offset, bwBufferChunks[i], BW_BUFFER_CHUNK_SIZE);
-  }
-
-  return true;
-}
-
-void GfxRenderer::freeStoredBwBuffer() { freeBwBufferChunks(); }
-
 /**
  * Copy stored BW buffer to framebuffer without freeing the stored chunks.
  * Use this when you want to restore the buffer but keep it for later reuse.

lib/GfxRenderer/GfxRenderer.h

@@ -67,6 +67,8 @@ class GfxRenderer {
   void fillRect(int x, int y, int width, int height, bool state = true) const;
   void drawImage(const uint8_t bitmap[], int x, int y, int width, int height) const;
   void drawBitmap(const Bitmap& bitmap, int x, int y, int maxWidth, int maxHeight) const;
+  void drawBitmap1Bit(const Bitmap& bitmap, int x, int y, int maxWidth, int maxHeight) const;
+  void fillPolygon(const int* xPoints, const int* yPoints, int numPoints, bool state = true) const;
 
   // Text
   int getTextWidth(int fontId, const char* text, EpdFontFamily::Style style = EpdFontFamily::REGULAR) const;

lib/JpegToBmpConverter/JpegToBmpConverter.cpp

@@ -114,6 +114,96 @@ static inline uint8_t quantize(int gray, int x, int y) {
   }
 }
 
+// 1-bit noise dithering for fast home screen rendering
+// Uses hash-based noise for consistent dithering that works well at small sizes
+static inline uint8_t quantize1bit(int gray, int x, int y) {
+  gray = adjustPixel(gray);
+
+  // Generate noise threshold using integer hash (no regular pattern to alias)
+  uint32_t hash = static_cast<uint32_t>(x) * 374761393u + static_cast<uint32_t>(y) * 668265263u;
+  hash = (hash ^ (hash >> 13)) * 1274126177u;
+  const int threshold = static_cast<int>(hash >> 24);  // 0-255
+
+  // Simple threshold with noise: gray >= (128 + noise offset) -> white
+  // The noise adds variation around the 128 midpoint
+  const int adjustedThreshold = 128 + ((threshold - 128) / 2);  // Range: 64-192
+  return (gray >= adjustedThreshold) ? 1 : 0;
+}
+
+// 1-bit Atkinson dithering - better quality than noise dithering for thumbnails
+// Error distribution pattern (same as 2-bit but quantizes to 2 levels):
+//     X  1/8 1/8
+// 1/8 1/8 1/8
+//     1/8
+class Atkinson1BitDitherer {
+ public:
+  Atkinson1BitDitherer(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
+  }
+
+  ~Atkinson1BitDitherer() {
+    delete[] errorRow0;
+    delete[] errorRow1;
+    delete[] errorRow2;
+  }
+
+  uint8_t processPixel(int gray, int x) {
+    // Apply brightness/contrast/gamma adjustments
+    gray = adjustPixel(gray);
+
+    // Add accumulated error
+    int adjusted = gray + errorRow0[x + 2];
+    if (adjusted < 0) adjusted = 0;
+    if (adjusted > 255) adjusted = 255;
+
+    // Quantize to 2 levels (1-bit): 0 = black, 1 = white
+    uint8_t quantized;
+    int quantizedValue;
+    if (adjusted < 128) {
+      quantized = 0;
+      quantizedValue = 0;
+    } else {
+      quantized = 1;
+      quantizedValue = 255;
+    }
+
+    // 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;
+};
+
 // Atkinson dithering - distributes only 6/8 (75%) of error for cleaner results
 // Error distribution pattern:
 //     X  1/8 1/8
@@ -355,6 +445,45 @@ void writeBmpHeader8bit(Print& bmpOut, const int width, const int height) {
   }
 }
 
+// Helper function: Write BMP header with 1-bit color depth (black and white)
+static void writeBmpHeader1bit(Print& bmpOut, const int width, const int height) {
+  // Calculate row padding (each row must be multiple of 4 bytes)
+  const int bytesPerRow = (width + 31) / 32 * 4;  // 1 bit per pixel, round up to 4-byte boundary
+  const int imageSize = bytesPerRow * height;
+  const uint32_t fileSize = 62 + imageSize;  // 14 (file header) + 40 (DIB header) + 8 (palette) + image
+
+  // BMP File Header (14 bytes)
+  bmpOut.write('B');
+  bmpOut.write('M');
+  write32(bmpOut, fileSize);  // File size
+  write32(bmpOut, 0);         // Reserved
+  write32(bmpOut, 62);        // Offset to pixel data (14 + 40 + 8)
+
+  // DIB Header (BITMAPINFOHEADER - 40 bytes)
+  write32(bmpOut, 40);
+  write32Signed(bmpOut, width);
+  write32Signed(bmpOut, -height);  // Negative height = top-down bitmap
+  write16(bmpOut, 1);              // Color planes
+  write16(bmpOut, 1);              // Bits per pixel (1 bit)
+  write32(bmpOut, 0);              // BI_RGB (no compression)
+  write32(bmpOut, imageSize);
+  write32(bmpOut, 2835);  // xPixelsPerMeter (72 DPI)
+  write32(bmpOut, 2835);  // yPixelsPerMeter (72 DPI)
+  write32(bmpOut, 2);     // colorsUsed
+  write32(bmpOut, 2);     // colorsImportant
+
+  // Color Palette (2 colors x 4 bytes = 8 bytes)
+  // Format: Blue, Green, Red, Reserved (BGRA)
+  // Note: In 1-bit BMP, palette index 0 = black, 1 = white
+  uint8_t palette[8] = {
+      0x00, 0x00, 0x00, 0x00,  // Color 0: Black
+      0xFF, 0xFF, 0xFF, 0x00   // Color 1: White
+  };
+  for (const uint8_t i : palette) {
+    bmpOut.write(i);
+  }
+}
+
 // Helper function: Write BMP header with 2-bit color depth
 static void writeBmpHeader2bit(Print& bmpOut, const int width, const int height) {
   // Calculate row padding (each row must be multiple of 4 bytes)
@@ -427,10 +556,11 @@ unsigned char JpegToBmpConverter::jpegReadCallback(unsigned char* pBuf, const un
   return 0;  // Success
 }
 
-// Internal implementation with configurable target size
+// Internal implementation with configurable target size and bit depth
-bool JpegToBmpConverter::jpegFileToBmpStreamInternal(FsFile& jpegFile, Print& bmpOut, int targetWidth,
+bool JpegToBmpConverter::jpegFileToBmpStreamInternal(FsFile& jpegFile, Print& bmpOut, int targetWidth, int targetHeight,
-                                                     int targetHeight) {
+                                                     bool oneBit) {
-  Serial.printf("[%lu] [JPG] Converting JPEG to BMP (target: %dx%d)\n", millis(), targetWidth, targetHeight);
+  Serial.printf("[%lu] [JPG] Converting JPEG to %s BMP (target: %dx%d)\n", millis(), oneBit ? "1-bit" : "2-bit",
+                targetWidth, targetHeight);
 
   // Setup context for picojpeg callback
   JpegReadContext context = {.file = jpegFile, .bufferPos = 0, .bufferFilled = 0};
@@ -490,9 +620,12 @@ bool JpegToBmpConverter::jpegFileToBmpStreamInternal(FsFile& jpegFile, Print& bm
 
   // Write BMP header with output dimensions
   int bytesPerRow;
-  if (USE_8BIT_OUTPUT) {
+  if (USE_8BIT_OUTPUT && !oneBit) {
     writeBmpHeader8bit(bmpOut, outWidth, outHeight);
     bytesPerRow = (outWidth + 3) / 4 * 4;
+  } else if (oneBit) {
+    writeBmpHeader1bit(bmpOut, outWidth, outHeight);
+    bytesPerRow = (outWidth + 31) / 32 * 4;  // 1 bit per pixel
   } else {
     writeBmpHeader2bit(bmpOut, outWidth, outHeight);
     bytesPerRow = (outWidth * 2 + 31) / 32 * 4;
@@ -525,11 +658,16 @@ bool JpegToBmpConverter::jpegFileToBmpStreamInternal(FsFile& jpegFile, Print& bm
     return false;
   }
 
-  // Create ditherer if enabled (only for 2-bit output)
+  // Create ditherer if enabled
   // Use OUTPUT dimensions for dithering (after prescaling)
   AtkinsonDitherer* atkinsonDitherer = nullptr;
   FloydSteinbergDitherer* fsDitherer = nullptr;
-  if (!USE_8BIT_OUTPUT) {
+  Atkinson1BitDitherer* atkinson1BitDitherer = nullptr;
+
+  if (oneBit) {
+    // For 1-bit output, use Atkinson dithering for better quality
+    atkinson1BitDitherer = new Atkinson1BitDitherer(outWidth);
+  } else if (!USE_8BIT_OUTPUT) {
     if (USE_ATKINSON) {
       atkinsonDitherer = new AtkinsonDitherer(outWidth);
     } else if (USE_FLOYD_STEINBERG) {
@@ -615,12 +753,24 @@ bool JpegToBmpConverter::jpegFileToBmpStreamInternal(FsFile& jpegFile, Print& bm
         // No scaling - direct output (1:1 mapping)
         memset(rowBuffer, 0, bytesPerRow);
 
-        if (USE_8BIT_OUTPUT) {
+        if (USE_8BIT_OUTPUT && !oneBit) {
           for (int x = 0; x < outWidth; x++) {
             const uint8_t gray = mcuRowBuffer[bufferY * imageInfo.m_width + x];
             rowBuffer[x] = adjustPixel(gray);
           }
+        } else if (oneBit) {
+          // 1-bit output with Atkinson dithering for better quality
+          for (int x = 0; x < outWidth; x++) {
+            const uint8_t gray = mcuRowBuffer[bufferY * imageInfo.m_width + x];
+            const uint8_t bit = atkinson1BitDitherer ? atkinson1BitDitherer->processPixel(gray, x) : quantize1bit(gray, x, y);
+            // Pack 1-bit value: MSB first, 8 pixels per byte
+            const int byteIndex = x / 8;
+            const int bitOffset = 7 - (x % 8);
+            rowBuffer[byteIndex] |= (bit << bitOffset);
+          }
+          if (atkinson1BitDitherer) atkinson1BitDitherer->nextRow();
         } else {
+          // 2-bit output
           for (int x = 0; x < outWidth; x++) {
             const uint8_t gray = mcuRowBuffer[bufferY * imageInfo.m_width + x];
             uint8_t twoBit;
@@ -678,12 +828,24 @@ bool JpegToBmpConverter::jpegFileToBmpStreamInternal(FsFile& jpegFile, Print& bm
         if (srcY_fp >= nextOutY_srcStart && currentOutY < outHeight) {
           memset(rowBuffer, 0, bytesPerRow);
 
-          if (USE_8BIT_OUTPUT) {
+          if (USE_8BIT_OUTPUT && !oneBit) {
             for (int x = 0; x < outWidth; x++) {
               const uint8_t gray = (rowCount[x] > 0) ? (rowAccum[x] / rowCount[x]) : 0;
               rowBuffer[x] = adjustPixel(gray);
             }
+          } else if (oneBit) {
+            // 1-bit output with Atkinson dithering for better quality
+            for (int x = 0; x < outWidth; x++) {
+              const uint8_t gray = (rowCount[x] > 0) ? (rowAccum[x] / rowCount[x]) : 0;
+              const uint8_t bit = atkinson1BitDitherer ? atkinson1BitDitherer->processPixel(gray, x) : quantize1bit(gray, x, currentOutY);
+              // Pack 1-bit value: MSB first, 8 pixels per byte
+              const int byteIndex = x / 8;
+              const int bitOffset = 7 - (x % 8);
+              rowBuffer[byteIndex] |= (bit << bitOffset);
+            }
+            if (atkinson1BitDitherer) atkinson1BitDitherer->nextRow();
           } else {
+            // 2-bit output
             for (int x = 0; x < outWidth; x++) {
               const uint8_t gray = (rowCount[x] > 0) ? (rowAccum[x] / rowCount[x]) : 0;
               uint8_t twoBit;
@@ -731,6 +893,9 @@ bool JpegToBmpConverter::jpegFileToBmpStreamInternal(FsFile& jpegFile, Print& bm
   if (fsDitherer) {
     delete fsDitherer;
   }
+  if (atkinson1BitDitherer) {
+    delete atkinson1BitDitherer;
+  }
   free(mcuRowBuffer);
   free(rowBuffer);
 
@@ -740,11 +905,17 @@ bool JpegToBmpConverter::jpegFileToBmpStreamInternal(FsFile& jpegFile, Print& bm
 
 // Core function: Convert JPEG file to 2-bit BMP (uses default target size)
 bool JpegToBmpConverter::jpegFileToBmpStream(FsFile& jpegFile, Print& bmpOut) {
-  return jpegFileToBmpStreamInternal(jpegFile, bmpOut, TARGET_MAX_WIDTH, TARGET_MAX_HEIGHT);
+  return jpegFileToBmpStreamInternal(jpegFile, bmpOut, TARGET_MAX_WIDTH, TARGET_MAX_HEIGHT, false);
 }
 
-// Convert with custom target size (for thumbnails)
+// Convert with custom target size (for thumbnails, 2-bit)
 bool JpegToBmpConverter::jpegFileToBmpStreamWithSize(FsFile& jpegFile, Print& bmpOut, int targetMaxWidth,
                                                      int targetMaxHeight) {
-  return jpegFileToBmpStreamInternal(jpegFile, bmpOut, targetMaxWidth, targetMaxHeight);
+  return jpegFileToBmpStreamInternal(jpegFile, bmpOut, targetMaxWidth, targetMaxHeight, false);
+}
+
+// Convert to 1-bit BMP (black and white only, no grays) for fast home screen rendering
+bool JpegToBmpConverter::jpegFileTo1BitBmpStreamWithSize(FsFile& jpegFile, Print& bmpOut, int targetMaxWidth,
+                                                          int targetMaxHeight) {
+  return jpegFileToBmpStreamInternal(jpegFile, bmpOut, targetMaxWidth, targetMaxHeight, true);
 }

lib/JpegToBmpConverter/JpegToBmpConverter.h

@@ -5,13 +5,15 @@ class Print;
 class ZipFile;
 
 class JpegToBmpConverter {
-  // [COMMENTED OUT] static uint8_t grayscaleTo2Bit(uint8_t grayscale, int x, int y);
   static unsigned char jpegReadCallback(unsigned char* pBuf, unsigned char buf_size,
                                         unsigned char* pBytes_actually_read, void* pCallback_data);
-  static bool jpegFileToBmpStreamInternal(class FsFile& jpegFile, Print& bmpOut, int targetWidth, int targetHeight);
+  static bool jpegFileToBmpStreamInternal(class FsFile& jpegFile, Print& bmpOut, int targetWidth, int targetHeight,
+                                          bool oneBit);
 
  public:
   static bool jpegFileToBmpStream(FsFile& jpegFile, Print& bmpOut);
   // Convert with custom target size (for thumbnails)
   static bool jpegFileToBmpStreamWithSize(FsFile& jpegFile, Print& bmpOut, int targetMaxWidth, int targetMaxHeight);
+  // Convert to 1-bit BMP (black and white only, no grays) for fast home screen rendering
+  static bool jpegFileTo1BitBmpStreamWithSize(FsFile& jpegFile, Print& bmpOut, int targetMaxWidth, int targetMaxHeight);
 };

lib/Xtc/Xtc.cpp

@@ -383,7 +383,7 @@ bool Xtc::generateThumbBmp() const {
     return false;
   }
 
-  // Create thumbnail BMP file - use 2-bit format like EPUB covers
+  // Create thumbnail BMP file - use 1-bit format for fast home screen rendering (no gray passes)
   FsFile thumbBmp;
   if (!SdMan.openFileForWrite("XTC", getThumbBmpPath(), thumbBmp)) {
     Serial.printf("[%lu] [XTC] Failed to create thumb BMP file\n", millis());
@@ -391,10 +391,10 @@ bool Xtc::generateThumbBmp() const {
     return false;
   }
 
-  // Write 2-bit BMP header (same format as JpegToBmpConverter)
+  // Write 1-bit BMP header for fast home screen rendering
-  const uint32_t rowSize = (thumbWidth * 2 + 31) / 32 * 4;  // 2 bits per pixel, aligned
+  const uint32_t rowSize = (thumbWidth + 31) / 32 * 4;  // 1 bit per pixel, aligned to 4 bytes
   const uint32_t imageSize = rowSize * thumbHeight;
-  const uint32_t fileSize = 14 + 40 + 16 + imageSize;  // 16 bytes for 4-color palette
+  const uint32_t fileSize = 14 + 40 + 8 + imageSize;  // 8 bytes for 2-color palette
 
   // File header
   thumbBmp.write('B');
@@ -402,7 +402,7 @@ bool Xtc::generateThumbBmp() const {
   thumbBmp.write(reinterpret_cast<const uint8_t*>(&fileSize), 4);
   uint32_t reserved = 0;
   thumbBmp.write(reinterpret_cast<const uint8_t*>(&reserved), 4);
-  uint32_t dataOffset = 14 + 40 + 16;  // 2-bit palette has 4 colors (16 bytes)
+  uint32_t dataOffset = 14 + 40 + 8;  // 1-bit palette has 2 colors (8 bytes)
   thumbBmp.write(reinterpret_cast<const uint8_t*>(&dataOffset), 4);
 
   // DIB header
@@ -414,7 +414,7 @@ bool Xtc::generateThumbBmp() const {
   thumbBmp.write(reinterpret_cast<const uint8_t*>(&heightVal), 4);
   uint16_t planes = 1;
   thumbBmp.write(reinterpret_cast<const uint8_t*>(&planes), 2);
-  uint16_t bitsPerPixel = 2;  // 2-bit for 4 grayscale levels
+  uint16_t bitsPerPixel = 1;  // 1-bit for black and white
   thumbBmp.write(reinterpret_cast<const uint8_t*>(&bitsPerPixel), 2);
   uint32_t compression = 0;
   thumbBmp.write(reinterpret_cast<const uint8_t*>(&compression), 4);
@@ -423,22 +423,19 @@ bool Xtc::generateThumbBmp() const {
   thumbBmp.write(reinterpret_cast<const uint8_t*>(&ppmX), 4);
   int32_t ppmY = 2835;
   thumbBmp.write(reinterpret_cast<const uint8_t*>(&ppmY), 4);
-  uint32_t colorsUsed = 4;
+  uint32_t colorsUsed = 2;
   thumbBmp.write(reinterpret_cast<const uint8_t*>(&colorsUsed), 4);
-  uint32_t colorsImportant = 4;
+  uint32_t colorsImportant = 2;
   thumbBmp.write(reinterpret_cast<const uint8_t*>(&colorsImportant), 4);
 
-  // Color palette (4 colors for 2-bit, same as JpegToBmpConverter)
+  // Color palette (2 colors for 1-bit: black and white)
-  uint8_t palette[16] = {
+  uint8_t palette[8] = {
       0x00, 0x00, 0x00, 0x00,  // Color 0: Black
-      0x55, 0x55, 0x55, 0x00,  // Color 1: Dark gray (85)
+      0xFF, 0xFF, 0xFF, 0x00   // Color 1: White
-      0xAA, 0xAA, 0xAA, 0x00,  // Color 2: Light gray (170)
-      0xFF, 0xFF, 0xFF, 0x00   // Color 3: White
   };
-  thumbBmp.write(palette, 16);
+  thumbBmp.write(palette, 8);
 
-  // Allocate row buffer for 2-bit output
+  // Allocate row buffer for 1-bit output
-  const size_t dstRowSize = (thumbWidth * 2 + 7) / 8;
   uint8_t* rowBuffer = static_cast<uint8_t*>(malloc(rowSize));
   if (!rowBuffer) {
     free(pageBuffer);
@@ -457,7 +454,7 @@ bool Xtc::generateThumbBmp() const {
   const size_t srcRowBytes = (bitDepth == 1) ? ((pageInfo.width + 7) / 8) : 0;
 
   for (uint16_t dstY = 0; dstY < thumbHeight; dstY++) {
-    memset(rowBuffer, 0xFF, rowSize);  // Start with all white (color 3)
+    memset(rowBuffer, 0xFF, rowSize);  // Start with all white (bit 1)
 
     // Calculate source Y range with bounds checking
     uint32_t srcYStart = (static_cast<uint32_t>(dstY) * scaleInv_fp) >> 16;
@@ -519,28 +516,28 @@ bool Xtc::generateThumbBmp() const {
         }
       }
 
-      // Calculate average grayscale and quantize to 2-bit
+      // Calculate average grayscale and quantize to 1-bit with noise dithering
       uint8_t avgGray = (totalCount > 0) ? static_cast<uint8_t>(graySum / totalCount) : 255;
 
-      // Quantize to 4 levels (same thresholds as JpegToBmpConverter)
+      // Hash-based noise dithering for 1-bit output
-      uint8_t twoBit;
+      uint32_t hash = static_cast<uint32_t>(dstX) * 374761393u + static_cast<uint32_t>(dstY) * 668265263u;
-      if (avgGray < 43) {
+      hash = (hash ^ (hash >> 13)) * 1274126177u;
-        twoBit = 0;  // Black
+      const int threshold = static_cast<int>(hash >> 24);  // 0-255
-      } else if (avgGray < 128) {
+      const int adjustedThreshold = 128 + ((threshold - 128) / 2);  // Range: 64-192
-        twoBit = 1;  // Dark gray
-      } else if (avgGray < 213) {
-        twoBit = 2;  // Light gray
-      } else {
-        twoBit = 3;  // White
-      }
 
-      // Pack 2-bit value into row buffer (MSB first)
+      // Quantize to 1-bit: 0=black, 1=white
-      const size_t byteIndex = (dstX * 2) / 8;
+      uint8_t oneBit = (avgGray >= adjustedThreshold) ? 1 : 0;
-      const size_t bitOffset = 6 - ((dstX * 2) % 8);
+
+      // Pack 1-bit value into row buffer (MSB first, 8 pixels per byte)
+      const size_t byteIndex = dstX / 8;
+      const size_t bitOffset = 7 - (dstX % 8);
       // Bounds check for row buffer access
       if (byteIndex < rowSize) {
-        rowBuffer[byteIndex] &= ~(0x03 << bitOffset);   // Clear bits
+        if (oneBit) {
-        rowBuffer[byteIndex] |= (twoBit << bitOffset);  // Set bits
+          rowBuffer[byteIndex] |= (1 << bitOffset);   // Set bit for white
+        } else {
+          rowBuffer[byteIndex] &= ~(1 << bitOffset);  // Clear bit for black
+        }
       }
     }
 

src/activities/home/HomeActivity.cpp

@@ -211,12 +211,18 @@ void HomeActivity::render() {
   constexpr int bookY = 30;
   const bool bookSelected = hasContinueReading && selectorIndex == 0;
 
+  // Bookmark dimensions (used in multiple places)
+  const int bookmarkWidth = bookWidth / 8;
+  const int bookmarkHeight = bookHeight / 5;
+  const int bookmarkX = bookX + bookWidth - bookmarkWidth - 10;
+  const int bookmarkY = bookY + 5;
+
   // Draw book card regardless, fill with message based on `hasContinueReading`
   {
     // Draw cover image as background if available (inside the box)
     // Only load from SD on first render, then use stored buffer
     if (hasContinueReading && hasCoverImage && !coverBmpPath.empty() && !coverRendered) {
-      // First time: load cover from SD and store buffer
+      // First time: load cover from SD and render
       FsFile file;
       if (SdMan.openFileForRead("HOME", coverBmpPath, file)) {
         Bitmap bitmap(file);
@@ -246,9 +252,39 @@ void HomeActivity::render() {
           // Draw border around the card
           renderer.drawRect(bookX, bookY, bookWidth, bookHeight);
 
-          coverRendered = true;
+          // Draw bookmark ribbon immediately after cover
-          // Store the buffer with cover image for fast navigation
+          const int notchDepth = bookmarkHeight / 3;
+          const int centerX = bookmarkX + bookmarkWidth / 2;
+
+          const int xPoints[5] = {
+              bookmarkX,                      // top-left
+              bookmarkX + bookmarkWidth,      // top-right
+              bookmarkX + bookmarkWidth,      // bottom-right
+              centerX,                        // center notch point
+              bookmarkX                       // bottom-left
+          };
+          const int yPoints[5] = {
+              bookmarkY,                              // top-left
+              bookmarkY,                              // top-right
+              bookmarkY + bookmarkHeight,             // bottom-right
+              bookmarkY + bookmarkHeight - notchDepth,  // center notch point
+              bookmarkY + bookmarkHeight              // bottom-left
+          };
+
+          // Draw bookmark ribbon (white normally, will be inverted if selected)
+          renderer.fillPolygon(xPoints, yPoints, 5, false);
+
+          // Store the buffer with cover image AND bookmark for fast navigation
           coverBufferStored = renderer.storeBwBuffer();
+          coverRendered = true;
+
+          // First render: if selected, draw selection indicators now
+          if (bookSelected) {
+            renderer.drawRect(bookX + 1, bookY + 1, bookWidth - 2, bookHeight - 2);
+            renderer.drawRect(bookX + 2, bookY + 2, bookWidth - 4, bookHeight - 4);
+            // Invert bookmark to black
+            renderer.fillPolygon(xPoints, yPoints, 5, true);
+          }
         }
         file.close();
       }
@@ -261,10 +297,33 @@ void HomeActivity::render() {
       }
     }
 
-    // If buffer was restored, just draw selection border if needed
+    // If buffer was restored, draw selection indicators if needed
-    if (bufferRestored && bookSelected) {
+    if (bufferRestored && bookSelected && coverRendered) {
+      // Draw selection border
       renderer.drawRect(bookX + 1, bookY + 1, bookWidth - 2, bookHeight - 2);
       renderer.drawRect(bookX + 2, bookY + 2, bookWidth - 4, bookHeight - 4);
+
+      // Invert bookmark color when selected (draw black over the white bookmark)
+      const int notchDepth = bookmarkHeight / 3;
+      const int centerX = bookmarkX + bookmarkWidth / 2;
+
+      const int xPoints[5] = {
+          bookmarkX,                      // top-left
+          bookmarkX + bookmarkWidth,      // top-right
+          bookmarkX + bookmarkWidth,      // bottom-right
+          centerX,                        // center notch point
+          bookmarkX                       // bottom-left
+      };
+      const int yPoints[5] = {
+          bookmarkY,                              // top-left
+          bookmarkY,                              // top-right
+          bookmarkY + bookmarkHeight,             // bottom-right
+          bookmarkY + bookmarkHeight - notchDepth,  // center notch point
+          bookmarkY + bookmarkHeight              // bottom-left
+      };
+
+      // Draw black filled bookmark ribbon (inverted)
+      renderer.fillPolygon(xPoints, yPoints, 5, true);
     } else if (!coverRendered) {
       // No cover: draw border for non-cover case
       renderer.drawRect(bookX, bookY, bookWidth, bookHeight);
@@ -273,33 +332,6 @@ void HomeActivity::render() {
         renderer.drawRect(bookX + 2, bookY + 2, bookWidth - 4, bookHeight - 4);
       }
     }
-
-    // Bookmark icon in the top-right corner of the card (inside the box)
-    // Skip if buffer was restored (bookmark is already in the buffer)
-    if (!bufferRestored) {
-      const int bookmarkWidth = bookWidth / 8;
-      const int bookmarkHeight = bookHeight / 5;
-      const int bookmarkX = bookX + bookWidth - bookmarkWidth - 10;
-      const int bookmarkY = bookY + 5;
-
-      // Main bookmark body (solid) - white on cover, inverted on selection
-      const bool bookmarkWhite = coverRendered ? true : !bookSelected;
-      renderer.fillRect(bookmarkX, bookmarkY, bookmarkWidth, bookmarkHeight, bookmarkWhite);
-
-      // Carve out an inverted triangle notch at the bottom center to create angled points
-      const int notchHeight = bookmarkHeight / 2;  // depth of the notch
-      const bool notchColor = coverRendered ? false : bookSelected;
-      for (int i = 0; i < notchHeight; ++i) {
-        const int y = bookmarkY + bookmarkHeight - 1 - i;
-        const int xStart = bookmarkX + i;
-        const int width = bookmarkWidth - 2 * i;
-        if (width <= 0) {
-          break;
-        }
-        // Draw a horizontal strip in the opposite color to "cut" the notch
-        renderer.fillRect(xStart, y, width, 1, notchColor);
-      }
-    }
   }
 
   if (hasContinueReading) {