feat: Extend high contrast mode to entire UI

- Add global high contrast mode flag in BitmapHelpers
- Modify quantization thresholds for high contrast rendering
- Update ditherer classes (Atkinson, Floyd-Steinberg) for contrast mode
- Add displayContrast setting with persistence
- Add "High Contrast" toggle in display settings
- Apply high contrast mode on startup from saved settings

src/CrossPointSettings.cpp

@@ -23,7 +23,7 @@ void readAndValidate(FsFile& file, uint8_t& member, const uint8_t maxValue) {
 namespace {
 constexpr uint8_t SETTINGS_FILE_VERSION = 1;
 // Increment this when adding new persisted settings fields
-constexpr uint8_t SETTINGS_COUNT = 26;  // 25 + sleepScreenCoverFilter
+constexpr uint8_t SETTINGS_COUNT = 27;  // 26 + displayContrast
 constexpr char SETTINGS_FILE[] = "/.crosspoint/settings.bin";
 }  // namespace
 
@@ -66,6 +66,8 @@ bool CrossPointSettings::saveToFile() const {
   serialization::writeString(outputFile, std::string(opdsPassword));
   // PR #476: B&W filter for cover images
   serialization::writePod(outputFile, sleepScreenCoverFilter);
+  // System-wide display contrast
+  serialization::writePod(outputFile, displayContrast);
   // New fields added at end for backward compatibility
   outputFile.close();
 
@@ -167,6 +169,9 @@ bool CrossPointSettings::loadFromFile() {
     // PR #476: B&W filter for cover images
     readAndValidate(inputFile, sleepScreenCoverFilter, SLEEP_SCREEN_COVER_FILTER_COUNT);
     if (++settingsRead >= fileSettingsCount) break;
+    // System-wide display contrast (0 = normal, 1 = high)
+    serialization::readPod(inputFile, displayContrast);
+    if (++settingsRead >= fileSettingsCount) break;
     // New fields added at end for backward compatibility
   } while (false);
 

src/CrossPointSettings.h

@@ -133,6 +133,8 @@ class CrossPointSettings {
   uint8_t hideBatteryPercentage = HIDE_NEVER;
   // Long-press chapter skip on side buttons
   uint8_t longPressChapterSkip = 1;
+  // System-wide display contrast (0 = normal, 1 = high)
+  uint8_t displayContrast = 0;
 
   // Pinned list name (empty = none pinned)
   char pinnedListName[64] = "";

src/activities/settings/CategorySettingsActivity.cpp

@@ -1,5 +1,6 @@
 #include "CategorySettingsActivity.h"
 
+#include <BitmapHelpers.h>
 #include <GfxRenderer.h>
 #include <HardwareSerial.h>
 
@@ -115,6 +116,11 @@ void CategorySettingsActivity::toggleCurrentSetting() {
     // Toggle the boolean value using the member pointer
     const bool currentValue = SETTINGS.*(setting.valuePtr);
     SETTINGS.*(setting.valuePtr) = !currentValue;
+
+    // Handle side effects for specific settings
+    if (setting.valuePtr == &CrossPointSettings::displayContrast) {
+      setHighContrastMode(SETTINGS.displayContrast == 1);
+    }
   } else if (setting.type == SettingType::ENUM && setting.valuePtr != nullptr) {
     const uint8_t currentValue = SETTINGS.*(setting.valuePtr);
     SETTINGS.*(setting.valuePtr) = (currentValue + 1) % static_cast<uint8_t>(setting.enumValues.size());

src/activities/settings/SettingsActivity.cpp

@@ -19,6 +19,7 @@ const SettingInfo displaySettings[displaySettingsCount] = {
     SettingInfo::Enum("Sleep Screen Cover Mode", &CrossPointSettings::sleepScreenCoverMode, {"Fit", "Crop", "Actual"}),
     SettingInfo::Enum("Sleep Screen Cover Filter", &CrossPointSettings::sleepScreenCoverFilter,
                       {"None", "Contrast", "Inverted"}),
+    SettingInfo::Toggle("High Contrast", &CrossPointSettings::displayContrast),
     SettingInfo::Enum("Status Bar", &CrossPointSettings::statusBar,
                       {"None", "No Progress", "Full w/ Percentage", "Full w/ Progress Bar", "Progress Bar"}),
     SettingInfo::Enum("Hide Battery %", &CrossPointSettings::hideBatteryPercentage, {"Never", "In Reader", "Always"}),

src/main.cpp

@@ -6,9 +6,12 @@
 #include <SDCardManager.h>
 #include <SPI.h>
 #include <builtinFonts/all.h>
+#include <esp_heap_caps.h>
 
 #include <cstring>
 
+#include <BitmapHelpers.h>
+
 #include "Battery.h"
 #include "BookListStore.h"
 #include "CrossPointSettings.h"
@@ -470,6 +473,8 @@ void setup() {
   }
 
   SETTINGS.loadFromFile();
+  // Apply high contrast mode from settings
+  setHighContrastMode(SETTINGS.displayContrast == 1);
 
   if (isWakeupByPowerButton()) {
     // For normal wakeups, verify power button press duration