Add dithering algorithms

src/CrossPointSettings.h

@@ -137,6 +137,12 @@ class CrossPointSettings {
 
   // Image rendering in EPUB reader
   enum IMAGE_RENDERING { IMAGES_DISPLAY = 0, IMAGES_PLACEHOLDER = 1, IMAGES_SUPPRESS = 2, IMAGE_RENDERING_COUNT };
+  enum IMAGE_DITHERING {
+    IMAGE_DITHER_BAYER = 0,
+    IMAGE_DITHER_ATKINSON = 1,
+    IMAGE_DITHER_DIFFUSED_BAYER = 2,
+    IMAGE_DITHERING_COUNT
+  };
 
   // Timezone options (POSIX TZ rules for DST support)
   enum TIMEZONE {
@@ -223,6 +229,8 @@ class CrossPointSettings {
   uint8_t showHiddenFiles = 0;
   // Image rendering mode in EPUB reader
   uint8_t imageRendering = IMAGES_DISPLAY;
+  // Dithering mode for decoded images (EPUB/JPG/PNG)
+  uint8_t imageDithering = IMAGE_DITHER_BAYER;
   // Enable synthetic TOC fallback for malformed/sparse TOC books (1 = enabled, 0 = disabled)
   uint8_t syntheticTocFallback = 1;
   // Show clock in the reader status bar

src/SettingsList.h

@@ -69,6 +69,10 @@ inline const std::vector<SettingInfo>& getSettingsList() {
       SettingInfo::Enum(StrId::STR_IMAGES, &CrossPointSettings::imageRendering,
                         {StrId::STR_IMAGES_DISPLAY, StrId::STR_IMAGES_PLACEHOLDER, StrId::STR_IMAGES_SUPPRESS},
                         "imageRendering", StrId::STR_CAT_READER),
+      SettingInfo::Enum(
+          StrId::STR_IMAGE_DITHERING, &CrossPointSettings::imageDithering,
+          {StrId::STR_IMAGE_DITHER_BAYER, StrId::STR_IMAGE_DITHER_ATKINSON, StrId::STR_IMAGE_DITHER_DIFFUSED_BAYER},
+          "imageDithering", StrId::STR_CAT_READER),
       SettingInfo::Toggle(StrId::STR_CREATE_FALLBACK_FOR_INVALID_TOC, &CrossPointSettings::syntheticTocFallback,
                           "syntheticTocFallback", StrId::STR_CAT_READER),
       // --- Controls ---

src/activities/util/BmpViewerActivity.cpp

@@ -18,6 +18,8 @@
 namespace {
 constexpr const char* SLEEP_BMP_PATH = "/sleep.bmp";
 
+uint8_t normalizeImageDitherModeValue(uint8_t mode) { return static_cast<uint8_t>(imageDitherModeFromSetting(mode)); }
+
 bool isBmpFile(const std::string& path) { return FsHelpers::hasBmpExtension(path); }
 
 bool isSupportedImageFile(const std::string& path) {
@@ -53,7 +55,13 @@ void computeCenteredImagePlacement(const int imageWidth, const int imageHeight,
 }  // namespace
 
 BmpViewerActivity::BmpViewerActivity(GfxRenderer& renderer, MappedInputManager& mappedInput, std::string path)
-    : Activity("BmpViewer", renderer, mappedInput), filePath(std::move(path)) {}
+    : Activity("BmpViewer", renderer, mappedInput),
+      filePath(std::move(path)),
+      imageDitherMode(normalizeImageDitherModeValue(SETTINGS.imageDithering)) {}
+
+bool BmpViewerActivity::renderCurrentImage(const bool showControls) {
+  return isBmpFile(filePath) ? renderBmpImage(showControls) : renderDecodedImage(showControls);
+}
 
 void BmpViewerActivity::onEnter() {
   Activity::onEnter();
@@ -62,7 +70,7 @@ void BmpViewerActivity::onEnter() {
     return;
   }
 
-  const bool rendered = isBmpFile(filePath) ? renderBmpImage() : renderDecodedImage();
+  const bool rendered = renderCurrentImage();
   if (!rendered) {
     renderError("Could not render image");
   }
@@ -100,7 +108,8 @@ bool BmpViewerActivity::renderBmpImage(const bool showControls) {
   renderer.clearScreen();
   renderer.drawBitmap(bitmap, x, y, pageWidth, pageHeight, 0, 0);
   if (showControls) {
-    const auto labels = mappedInput.mapLabels(tr(STR_BACK), "", "", tr(STR_SET_SLEEP_SCREEN));
+    const auto labels =
+        mappedInput.mapLabels(tr(STR_BACK), "", I18N.get(getCurrentDitherModeLabel()), tr(STR_SET_SLEEP_SCREEN));
     GUI.drawButtonHints(renderer, labels.btn1, labels.btn2, labels.btn3, labels.btn4);
   }
   renderer.displayBuffer(HalDisplay::HALF_REFRESH);
@@ -139,19 +148,44 @@ bool BmpViewerActivity::renderDecodedImage(const bool showControls) {
   config.useExactDimensions = true;
   config.useGrayscale = true;
   config.useDithering = true;
+  config.ditherMode = imageDitherModeFromSetting(imageDitherMode);
 
   if (!decoder->decodeToFramebuffer(filePath, renderer, config)) {
     return false;
   }
 
   if (showControls) {
-    const auto labels = mappedInput.mapLabels(tr(STR_BACK), "", "", tr(STR_SET_SLEEP_SCREEN));
+    const auto labels =
+        mappedInput.mapLabels(tr(STR_BACK), "", I18N.get(getCurrentDitherModeLabel()), tr(STR_SET_SLEEP_SCREEN));
     GUI.drawButtonHints(renderer, labels.btn1, labels.btn2, labels.btn3, labels.btn4);
   }
   renderer.displayBuffer(HalDisplay::HALF_REFRESH);
   return true;
 }
 
+StrId BmpViewerActivity::getCurrentDitherModeLabel() const {
+  switch (imageDitherModeFromSetting(imageDitherMode)) {
+    case ImageDitherMode::Atkinson:
+      return StrId::STR_IMAGE_DITHER_ATKINSON;
+    case ImageDitherMode::DiffusedBayer:
+      return StrId::STR_IMAGE_DITHER_DIFFUSED_BAYER;
+    case ImageDitherMode::Bayer:
+    case ImageDitherMode::COUNT:
+    default:
+      return StrId::STR_IMAGE_DITHER_BAYER;
+  }
+}
+
+void BmpViewerActivity::cycleDitherMode() {
+  imageDitherMode = (imageDitherMode + 1) % CrossPointSettings::IMAGE_DITHERING_COUNT;
+  SETTINGS.imageDithering = imageDitherMode;
+  SETTINGS.saveToFile();
+
+  if (!renderCurrentImage()) {
+    renderError("Could not render image");
+  }
+}
+
 void BmpViewerActivity::renderError(const char* message) {
   const auto pageHeight = renderer.getScreenHeight();
   renderer.clearScreen();
@@ -210,6 +244,11 @@ void BmpViewerActivity::loop() {
     return;
   }
 
+  if (mappedInput.wasReleased(MappedInputManager::Button::Left)) {
+    cycleDitherMode();
+    return;
+  }
+
   // Next/Right button: set this image as the sleep screen
   if (mappedInput.wasReleased(MappedInputManager::Button::Right)) {
     setAsSleepScreen();

src/activities/util/BmpViewerActivity.h

@@ -1,5 +1,8 @@
 #pragma once
 
+#include <Epub/converters/ImageToFramebufferDecoder.h>
+#include <I18nKeys.h>
+
 #include <functional>
 #include <string>
 
@@ -16,8 +19,12 @@ class BmpViewerActivity final : public Activity {
 
  private:
   std::string filePath;
+  uint8_t imageDitherMode;
+  bool renderCurrentImage(bool showControls = true);
   bool renderBmpImage(bool showControls = true);
   bool renderDecodedImage(bool showControls = true);
+  void cycleDitherMode();
+  StrId getCurrentDitherModeLabel() const;
   void renderError(const char* message);
   void setAsSleepScreen();
-};
+};