Add 2-bit grayscale text and anti-aliased rendering of text

lib/EpdFont/EpdFontData.h

@@ -31,4 +31,5 @@ typedef struct {
   uint8_t advanceY;                     ///< Newline distance (y axis)
   int ascender;                         ///< Maximal height of a glyph above the base line
   int descender;                        ///< Maximal height of a glyph below the base line
+  bool is2Bit;
 } EpdFontData;

lib/EpdFont/builtinFonts/babyblue.h

@@ -2,6 +2,7 @@
  * generated by fontconvert.py
  * name: babyblue
  * size: 8
+ * mode: 1-bit
  */
 #pragma once
 #include "EpdFontData.h"
@@ -500,5 +501,5 @@ static const EpdUnicodeInterval babyblueIntervals[] = {
 };
 
 static const EpdFontData babyblue = {
-    babyblueBitmaps, babyblueGlyphs, babyblueIntervals, 5, 17, 13, -4,
+    babyblueBitmaps, babyblueGlyphs, babyblueIntervals, 5, 17, 13, -4, false,
 };

lib/EpdFont/builtinFonts/ubuntu_10.h

@@ -2,6 +2,7 @@
  * generated by fontconvert.py
  * name: ubuntu_10
  * size: 10
+ * mode: 1-bit
  */
 #pragma once
 #include "EpdFontData.h"
@@ -762,5 +763,5 @@ static const EpdUnicodeInterval ubuntu_10Intervals[] = {
 };
 
 static const EpdFontData ubuntu_10 = {
-    ubuntu_10Bitmaps, ubuntu_10Glyphs, ubuntu_10Intervals, 31, 24, 20, -4,
+    ubuntu_10Bitmaps, ubuntu_10Glyphs, ubuntu_10Intervals, 31, 24, 20, -4, false,
 };

lib/EpdFont/builtinFonts/ubuntu_bold_10.h

@@ -2,6 +2,7 @@
  * generated by fontconvert.py
  * name: ubuntu_bold_10
  * size: 10
+ * mode: 1-bit
  */
 #pragma once
 #include "EpdFontData.h"
@@ -806,5 +807,5 @@ static const EpdUnicodeInterval ubuntu_bold_10Intervals[] = {
 };
 
 static const EpdFontData ubuntu_bold_10 = {
-    ubuntu_bold_10Bitmaps, ubuntu_bold_10Glyphs, ubuntu_bold_10Intervals, 31, 24, 20, -4,
+    ubuntu_bold_10Bitmaps, ubuntu_bold_10Glyphs, ubuntu_bold_10Intervals, 31, 24, 20, -4, false,
 };

lib/EpdFont/scripts/fontconvert.py

@@ -13,12 +13,14 @@ parser = argparse.ArgumentParser(description="Generate a header file from a font
 parser.add_argument("name", action="store", help="name of the font.")
 parser.add_argument("size", type=int, help="font size to use.")
 parser.add_argument("fontstack", action="store", nargs='+', help="list of font files, ordered by descending priority.")
+parser.add_argument("--2bit", dest="is2Bit", action="store_true", help="generate 2-bit greyscale bitmap instead of 1-bit black and white.")
 parser.add_argument("--additional-intervals", dest="additional_intervals", action="append", help="Additional code point intervals to export as min,max. This argument can be repeated.")
 args = parser.parse_args()
 
 GlyphProps = namedtuple("GlyphProps", ["width", "height", "advance_x", "left", "top", "data_length", "data_offset", "code_point"])
 
 font_stack = [freetype.Face(f) for f in args.fontstack]
+is2Bit = args.is2Bit
 size = args.size
 font_name = args.name
 
@@ -173,26 +175,73 @@ for i_start, i_end in intervals:
                 pixels4g.append(px)
                 px = 0
 
-        # Downsample to 1-bit bitmap - treat any non-zero as black
-        pixelsbw = []
-        px = 0
-        pitch = (bitmap.width // 2) + (bitmap.width % 2)
-        for y in range(bitmap.rows):
-            for x in range(bitmap.width):
-                px = px << 1
-                bm = pixels4g[y * pitch + (x // 2)]
-                px += 1 if ((x & 1) == 0 and bm & 0xF > 0) or ((x & 1) == 1 and bm & 0xF0 > 0) else 0
+        if is2Bit:
+            # 0 = white, 15 black, 8+ dark grey, 7- light grey
+            # Downsample to 2-bit bitmap
+            pixels2b = []
+            px = 0
+            pitch = (bitmap.width // 2) + (bitmap.width % 2)
+            for y in range(bitmap.rows):
+                for x in range(bitmap.width):
+                    px = px << 2
+                    bm = pixels4g[y * pitch + (x // 2)]
+                    bm = (bm >> ((x % 2) * 4)) & 0xF
 
-                if (y * bitmap.width + x) % 8 == 7:
-                    pixelsbw.append(px)
-                    px = 0
-        if (bitmap.width * bitmap.rows) % 8 != 0:
-            px = px << (8 - (bitmap.width * bitmap.rows) % 8)
-            pixelsbw.append(px)
+                    if bm == 15:
+                        px += 3
+                    elif bm >= 8:
+                        px += 2
+                    elif bm > 0:
+                        px += 1
 
+                    if (y * bitmap.width + x) % 4 == 3:
+                        pixels2b.append(px)
+                        px = 0
+            if (bitmap.width * bitmap.rows) % 4 != 0:
+                px = px << (4 - (bitmap.width * bitmap.rows) % 4) * 2
+                pixels2b.append(px)
+
+            # for y in range(bitmap.rows):
+            #     line = ''
+            #     for x in range(bitmap.width):
+            #         pixelPosition = y * bitmap.width + x
+            #         byte = pixels2b[pixelPosition // 4]
+            #         bit_index = (3 - (pixelPosition % 4)) * 2
+            #         line += '#' if ((byte >> bit_index) & 3) > 0 else '.'
+            #     print(line)
+            # print('')
+        else:
+            # Downsample to 1-bit bitmap - treat any non-zero as black
+            pixelsbw = []
+            px = 0
+            pitch = (bitmap.width // 2) + (bitmap.width % 2)
+            for y in range(bitmap.rows):
+                for x in range(bitmap.width):
+                    px = px << 1
+                    bm = pixels4g[y * pitch + (x // 2)]
+                    px += 1 if ((x & 1) == 0 and bm & 0xF > 0) or ((x & 1) == 1 and bm & 0xF0 > 0) else 0
+
+                    if (y * bitmap.width + x) % 8 == 7:
+                        pixelsbw.append(px)
+                        px = 0
+            if (bitmap.width * bitmap.rows) % 8 != 0:
+                px = px << (8 - (bitmap.width * bitmap.rows) % 8)
+                pixelsbw.append(px)
+
+            # for y in range(bitmap.rows):
+            #     line = ''
+            #     for x in range(bitmap.width):
+            #         pixelPosition = y * bitmap.width + x
+            #         byte = pixelsbw[pixelPosition // 8]
+            #         bit_index = 7 - (pixelPosition % 8)
+            #         line += '#' if (byte >> bit_index) & 1 else '.'
+            #     print(line)
+            # print('')
+
+        pixels = pixels2b if is2Bit else pixelsbw
 
         # Build output data
-        packed = bytes(pixelsbw)
+        packed = bytes(pixels)
         glyph = GlyphProps(
             width = bitmap.width,
             height = bitmap.rows,
@@ -216,7 +265,7 @@ for index, glyph in enumerate(all_glyphs):
     glyph_data.extend([b for b in packed])
     glyph_props.append(props)
 
-print(f"/**\n * generated by fontconvert.py\n * name: {font_name}\n * size: {size}\n */")
+print(f"/**\n * generated by fontconvert.py\n * name: {font_name}\n * size: {size}\n * mode: {'2-bit' if is2Bit else '1-bit'}\n */")
 print("#pragma once")
 print("#include \"EpdFontData.h\"\n")
 print(f"static const uint8_t {font_name}Bitmaps[{len(glyph_data)}] = {{")
@@ -244,4 +293,5 @@ print(f"    {len(intervals)},")
 print(f"    {norm_ceil(face.size.height)},")
 print(f"    {norm_ceil(face.size.ascender)},")
 print(f"    {norm_floor(face.size.descender)},")
+print(f"    {'true' if is2Bit else 'false'},")
 print("};")

lib/EpdFontRenderer/EpdFontRenderer.hpp

@@ -6,23 +6,27 @@
 inline int min(const int a, const int b) { return a < b ? a : b; }
 inline int max(const int a, const int b) { return a > b ? a : b; }
 
+enum EpdFontRendererMode { BW, GRAYSCALE_LSB, GRAYSCALE_MSB };
+
 template <typename Renderable>
 class EpdFontRenderer {
   Renderable& renderer;
-  void renderChar(uint32_t cp, int* x, const int* y, bool pixelState, EpdFontStyle style = REGULAR);
+  void renderChar(uint32_t cp, int* x, const int* y, bool pixelState, EpdFontStyle style = REGULAR,
+                  EpdFontRendererMode mode = BW);
 
  public:
   const EpdFontFamily* fontFamily;
   explicit EpdFontRenderer(const EpdFontFamily* fontFamily, Renderable& renderer)
       : fontFamily(fontFamily), renderer(renderer) {}
   ~EpdFontRenderer() = default;
-  void renderString(const char* string, int* x, int* y, bool pixelState = true, EpdFontStyle style = REGULAR);
+  void renderString(const char* string, int* x, int* y, bool pixelState = true, EpdFontStyle style = REGULAR,
+                    EpdFontRendererMode mode = BW);
   void drawPixel(int x, int y, bool pixelState);
 };
 
 template <typename Renderable>
 void EpdFontRenderer<Renderable>::renderString(const char* string, int* x, int* y, const bool pixelState,
-                                               const EpdFontStyle style) {
+                                               const EpdFontStyle style, const EpdFontRendererMode mode) {
   // cannot draw a NULL / empty string
   if (string == nullptr || *string == '\0') {
     return;
@@ -35,7 +39,7 @@ void EpdFontRenderer<Renderable>::renderString(const char* string, int* x, int*
 
   uint32_t cp;
   while ((cp = utf8NextCodepoint(reinterpret_cast<const uint8_t**>(&string)))) {
-    renderChar(cp, x, y, pixelState, style);
+    renderChar(cp, x, y, pixelState, style, mode);
   }
 
   *y += fontFamily->getData(style)->advanceY;
@@ -77,7 +81,7 @@ void EpdFontRenderer<Renderable>::drawPixel(const int x, const int y, const bool
 
 template <typename Renderable>
 void EpdFontRenderer<Renderable>::renderChar(const uint32_t cp, int* x, const int* y, const bool pixelState,
-                                             const EpdFontStyle style) {
+                                             const EpdFontStyle style, const EpdFontRendererMode mode) {
   const EpdGlyph* glyph = fontFamily->getGlyph(cp, style);
   if (!glyph) {
     // TODO: Replace with fallback glyph property?
@@ -90,6 +94,7 @@ void EpdFontRenderer<Renderable>::renderChar(const uint32_t cp, int* x, const in
     return;
   }
 
+  const int is2Bit = fontFamily->getData(style)->is2Bit;
   const uint32_t offset = glyph->dataOffset;
   const uint8_t width = glyph->width;
   const uint8_t height = glyph->height;
@@ -105,11 +110,26 @@ void EpdFontRenderer<Renderable>::renderChar(const uint32_t cp, int* x, const in
         const int pixelPosition = glyphY * width + glyphX;
         int screenX = *x + left + glyphX;
 
-        const uint8_t byte = bitmap[pixelPosition / 8];
-        const uint8_t bit_index = 7 - (pixelPosition % 8);
+        if (is2Bit) {
+          const uint8_t byte = bitmap[pixelPosition / 4];
+          const uint8_t bit_index = (3 - pixelPosition % 4) * 2;
 
-        if ((byte >> bit_index) & 1) {
-          drawPixel(screenX, screenY, pixelState);
+          const uint8_t val = (byte >> bit_index) & 0x3;
+          if (mode == BW && val > 0) {
+            drawPixel(screenX, screenY, pixelState);
+          } else if (mode == GRAYSCALE_MSB && val == 1) {
+            // TODO: Not sure how this anti-aliasing goes on black backgrounds
+            drawPixel(screenX, screenY, false);
+          } else if (mode == GRAYSCALE_LSB && val == 2) {
+            drawPixel(screenX, screenY, false);
+          }
+        } else {
+          const uint8_t byte = bitmap[pixelPosition / 8];
+          const uint8_t bit_index = 7 - (pixelPosition % 8);
+
+          if ((byte >> bit_index) & 1) {
+            drawPixel(screenX, screenY, pixelState);
+          }
         }
       }
     }

lib/EpdRenderer/EpdRenderer.cpp

@@ -1,17 +1,17 @@
 #include "EpdRenderer.h"
 
 #include "builtinFonts/babyblue.h"
-#include "builtinFonts/bookerly.h"
-#include "builtinFonts/bookerly_bold.h"
-#include "builtinFonts/bookerly_bold_italic.h"
-#include "builtinFonts/bookerly_italic.h"
+#include "builtinFonts/bookerly_2b.h"
+#include "builtinFonts/bookerly_bold_2b.h"
+#include "builtinFonts/bookerly_bold_italic_2b.h"
+#include "builtinFonts/bookerly_italic_2b.h"
 #include "builtinFonts/ubuntu_10.h"
 #include "builtinFonts/ubuntu_bold_10.h"
 
-EpdFont bookerlyFont(&bookerly);
-EpdFont bookerlyBoldFont(&bookerly_bold);
-EpdFont bookerlyItalicFont(&bookerly_italic);
-EpdFont bookerlyBoldItalicFont(&bookerly_bold_italic);
+EpdFont bookerlyFont(&bookerly_2b);
+EpdFont bookerlyBoldFont(&bookerly_bold_2b);
+EpdFont bookerlyItalicFont(&bookerly_italic_2b);
+EpdFont bookerlyBoldItalicFont(&bookerly_bold_italic_2b);
 EpdFontFamily bookerlyFontFamily(&bookerlyFont, &bookerlyBoldFont, &bookerlyItalicFont, &bookerlyBoldItalicFont);
 
 EpdFont smallFont(&babyblue);
@@ -27,6 +27,7 @@ EpdRenderer::EpdRenderer(EInkDisplay& einkDisplay)
       marginBottom(30),
       marginLeft(10),
       marginRight(10),
+      fontRendererMode(BW),
       lineCompression(0.95f) {
   this->regularFontRenderer = new EpdFontRenderer<EInkDisplay>(&bookerlyFontFamily, einkDisplay);
   this->smallFontRenderer = new EpdFontRenderer<EInkDisplay>(&smallFontFamily, einkDisplay);
@@ -101,21 +102,21 @@ void EpdRenderer::drawText(const int x, const int y, const char* text, const boo
                            const EpdFontStyle style) const {
   int ypos = y + getLineHeight() + marginTop;
   int xpos = x + marginLeft;
-  regularFontRenderer->renderString(text, &xpos, &ypos, state, style);
+  regularFontRenderer->renderString(text, &xpos, &ypos, state, style, fontRendererMode);
 }
 
 void EpdRenderer::drawUiText(const int x, const int y, const char* text, const bool state,
                              const EpdFontStyle style) const {
   int ypos = y + uiFontRenderer->fontFamily->getData(style)->advanceY + marginTop;
   int xpos = x + marginLeft;
-  uiFontRenderer->renderString(text, &xpos, &ypos, state, style);
+  uiFontRenderer->renderString(text, &xpos, &ypos, state, style, fontRendererMode);
 }
 
 void EpdRenderer::drawSmallText(const int x, const int y, const char* text, const bool state,
                                 const EpdFontStyle style) const {
   int ypos = y + smallFontRenderer->fontFamily->getData(style)->advanceY + marginTop;
   int xpos = x + marginLeft;
-  smallFontRenderer->renderString(text, &xpos, &ypos, state, style);
+  smallFontRenderer->renderString(text, &xpos, &ypos, state, style, fontRendererMode);
 }
 
 void EpdRenderer::drawTextBox(const int x, const int y, const std::string& text, const int width, const int height,
@@ -221,3 +222,9 @@ int EpdRenderer::getSpaceWidth() const { return regularFontRenderer->fontFamily-
 int EpdRenderer::getLineHeight() const {
   return regularFontRenderer->fontFamily->getData(REGULAR)->advanceY * lineCompression;
 }
+
+void EpdRenderer::copyGrayscaleLsbBuffers() const { einkDisplay.copyGrayscaleLsbBuffers(einkDisplay.getFrameBuffer()); }
+
+void EpdRenderer::copyGrayscaleMsbBuffers() const { einkDisplay.copyGrayscaleMsbBuffers(einkDisplay.getFrameBuffer()); }
+
+void EpdRenderer::displayGrayBuffer() const { einkDisplay.displayGrayBuffer(); }

lib/EpdRenderer/EpdRenderer.h

@@ -13,6 +13,7 @@ class EpdRenderer {
   int marginBottom;
   int marginLeft;
   int marginRight;
+  EpdFontRendererMode fontRendererMode;
   float lineCompression;
 
  public:
@@ -32,6 +33,9 @@ class EpdRenderer {
   void drawImage(const uint8_t bitmap[], int x, int y, int width, int height) const;
   void drawImageNoMargin(const uint8_t bitmap[], int x, int y, int width, int height) const;
 
+  void copyGrayscaleLsbBuffers() const;
+  void copyGrayscaleMsbBuffers() const;
+  void displayGrayBuffer() const;
   void clearScreen(uint8_t color = 0xFF) const;
   void flushDisplay(bool partialUpdate = true) const;
   void flushArea(int x, int y, int width, int height) const;
@@ -46,4 +50,5 @@ class EpdRenderer {
   void setMarginBottom(const int newMarginBottom) { this->marginBottom = newMarginBottom; }
   void setMarginLeft(const int newMarginLeft) { this->marginLeft = newMarginLeft; }
   void setMarginRight(const int newMarginRight) { this->marginRight = newMarginRight; }
+  void setFontRendererMode(const EpdFontRendererMode mode) { this->fontRendererMode = mode; }
 };

lib/Epub/Epub/Section.cpp

@@ -98,21 +98,15 @@ bool Section::persistPageDataToSD() {
   return true;
 }
 
-void Section::renderPage() const {
-  if (0 <= currentPage && currentPage < pageCount) {
-    const auto filePath = "/sd" + cachePath + "/page_" + std::to_string(currentPage) + ".bin";
-    std::ifstream inputFile(filePath);
-    const Page* p = Page::deserialize(inputFile);
-    inputFile.close();
-    p->render(renderer);
-    delete p;
-  } else if (pageCount == 0) {
-    Serial.println("No pages to render");
-    const int width = renderer.getTextWidth("Empty chapter", BOLD);
-    renderer.drawText((renderer.getPageWidth() - width) / 2, 300, "Empty chapter", 1, BOLD);
-  } else {
-    Serial.printf("Page out of bounds: %d (max %d)\n", currentPage, pageCount);
-    const int width = renderer.getTextWidth("Out of bounds", BOLD);
-    renderer.drawText((renderer.getPageWidth() - width) / 2, 300, "Out of bounds", 1, BOLD);
+Page* Section::loadPageFromSD() const {
+  const auto filePath = "/sd" + cachePath + "/page_" + std::to_string(currentPage) + ".bin";
+  if (!SD.exists(filePath.c_str() + 3)) {
+    Serial.printf("Page file does not exist: %s\n", filePath.c_str());
+    return nullptr;
   }
+
+  std::ifstream inputFile(filePath);
+  Page* p = Page::deserialize(inputFile);
+  inputFile.close();
+  return p;
 }

lib/Epub/Epub/Section.h

@@ -26,5 +26,5 @@ class Section {
   void setupCacheDir() const;
   void clearCache() const;
   bool persistPageDataToSD();
-  void renderPage() const;
+  Page* loadPageFromSD() const;
 };

src/screens/EpubReaderScreen.cpp

@@ -1,6 +1,7 @@
 #include "EpubReaderScreen.h"
 
 #include <EpdRenderer.h>
+#include <Epub/Page.h>
 #include <SD.h>
 
 #include "Battery.h"
@@ -128,7 +129,7 @@ void EpubReaderScreen::displayTaskLoop() {
     if (updateRequired) {
       updateRequired = false;
       xSemaphoreTake(renderingMutex, portMAX_DELAY);
-      renderPage();
+      renderScreen();
       xSemaphoreGive(renderingMutex);
     }
     vTaskDelay(10 / portTICK_PERIOD_MS);
@@ -136,7 +137,7 @@ void EpubReaderScreen::displayTaskLoop() {
 }
 
 // TODO: Failure handling
-void EpubReaderScreen::renderPage() {
+void EpubReaderScreen::renderScreen() {
   if (!epub) {
     return;
   }
@@ -184,16 +185,27 @@ void EpubReaderScreen::renderPage() {
   }
 
   renderer.clearScreen();
-  section->renderPage();
-  renderStatusBar();
-  if (pagesUntilFullRefresh <= 1) {
-    renderer.flushDisplay(false);
-    pagesUntilFullRefresh = PAGES_PER_REFRESH;
-  } else {
+
+  if (section->pageCount == 0) {
+    Serial.println("No pages to render");
+    const int width = renderer.getTextWidth("Empty chapter", BOLD);
+    renderer.drawText((renderer.getPageWidth() - width) / 2, 300, "Empty chapter", true, BOLD);
     renderer.flushDisplay();
-    pagesUntilFullRefresh--;
+    return;
   }
 
+  if (section->currentPage < 0 || section->currentPage >= section->pageCount) {
+    Serial.printf("Page out of bounds: %d (max %d)\n", section->currentPage, section->pageCount);
+    const int width = renderer.getTextWidth("Out of bounds", BOLD);
+    renderer.drawText((renderer.getPageWidth() - width) / 2, 300, "Out of bounds", true, BOLD);
+    renderer.flushDisplay();
+    return;
+  }
+
+  const Page* p = section->loadPageFromSD();
+  renderContents(p);
+  delete p;
+
   File f = SD.open((epub->getCachePath() + "/progress.bin").c_str(), FILE_WRITE);
   uint8_t data[4];
   data[0] = currentSpineIndex & 0xFF;
@@ -204,6 +216,30 @@ void EpubReaderScreen::renderPage() {
   f.close();
 }
 
+void EpubReaderScreen::renderContents(const Page* p) const {
+  p->render(renderer);
+  renderStatusBar();
+  renderer.flushDisplay();
+
+  // grayscale rendering
+  {
+    renderer.clearScreen(0x00);
+    renderer.setFontRendererMode(GRAYSCALE_LSB);
+    p->render(renderer);
+    renderer.copyGrayscaleLsbBuffers();
+
+    // Render and copy to MSB buffer
+    renderer.clearScreen(0x00);
+    renderer.setFontRendererMode(GRAYSCALE_MSB);
+    p->render(renderer);
+    renderer.copyGrayscaleMsbBuffers();
+
+    // display grayscale part
+    renderer.displayGrayBuffer();
+    renderer.setFontRendererMode(BW);
+  }
+}
+
 void EpubReaderScreen::renderStatusBar() const {
   const auto pageWidth = renderer.getPageWidth();
 

src/screens/EpubReaderScreen.h

@@ -20,7 +20,8 @@ class EpubReaderScreen final : public Screen {
 
   static void taskTrampoline(void* param);
   [[noreturn]] void displayTaskLoop();
-  void renderPage();
+  void renderScreen();
+  void renderContents(const Page* p) const;
   void renderStatusBar() const;
 
  public: