Render larger images on demand not by default

src/CrossPointSettings.h

@@ -267,6 +267,9 @@ class CrossPointSettings {
   uint8_t showFileExtensions = 0;
   // Image rendering mode in EPUB reader
   uint8_t imageRendering = IMAGES_DISPLAY;
+  // Show a placeholder for large images (>800×600 source pixels) instead of decoding immediately.
+  // The user can press OK on the placeholder page to decode the image on demand.
+  uint8_t largeImagePlaceholder = 1;
   // Dithering mode for decoded images (EPUB/JPG/PNG)
   uint8_t imageDithering = IMAGE_DITHER_BAYER;
   // Tilt-based page turning (X3 only — requires QMI8658 IMU)

src/SettingsList.h

@@ -139,6 +139,8 @@ inline const std::vector<SettingInfo> list = {
     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::Toggle(StrId::STR_LARGE_IMAGE_PLACEHOLDER, &CrossPointSettings::largeImagePlaceholder,
+                        "largeImagePlaceholder", StrId::STR_CAT_READER),
     SettingInfo::Value(StrId::STR_SCREEN_MARGIN, &CrossPointSettings::screenMargin, {5, 40, 5}, "screenMargin",
                        StrId::STR_CAT_READER)
         .withSubmenu(StrId::STR_MENU_READER_SPACING),

src/activities/reader/EpubReaderActivity.cpp

@@ -407,6 +407,12 @@ void EpubReaderActivity::loop() {
         return;
       }
       if (ev.type == ButtonEventManager::PressType::Short) {
+        if (pageHasPlaceholders) {
+          forceLoadLargeImages = true;
+          pageHasPlaceholders = false;
+          requestUpdate();
+          return;
+        }
         openReaderMenu();
         return;
       }
@@ -1512,6 +1518,8 @@ bool EpubReaderActivity::stepPageState(const bool isForwardTurn) {
   }
 
   lastPageTurnTime = millis();
+  forceLoadLargeImages = false;
+  pageHasPlaceholders = false;
   return true;
 }
 
@@ -1868,15 +1876,18 @@ void EpubReaderActivity::renderContents(std::unique_ptr<Page> page, const int or
   }
   lastRenderStats.textAntiAliasing = aaEnabledForThisRender;
 
-  // Force special handling for pages with images when anti-aliasing is on
-  bool imagePageWithAA = page->hasImages() && aaEnabledForThisRender;
+  // Force special handling for pages with real (non-placeholder) images when anti-aliasing is on
+  bool imagePageWithAA = page->hasImages() && !pageHasPlaceholders && aaEnabledForThisRender;
   bool forceHalfRefreshThisPage = pendingHalfRefreshAfterImagePage && SETTINGS.halfRefreshAfterImagePage;
   pendingHalfRefreshAfterImagePage = false;
   lastRenderStats.imagePageWithAA = imagePageWithAA;
   lastRenderStats.forcedHalfRefresh = forceHalfRefreshThisPage;
 
+  const bool effectiveForceLoad = forceLoadLargeImages || !SETTINGS.largeImagePlaceholder;
+  pageHasPlaceholders = page->hasPlaceholderImages(effectiveForceLoad);
+
   logReaderMemSnapshot("before_bw_render");
-  page->render(renderer, getEffectiveReaderFontId(), orientedMarginLeft, contentTop);
+  page->render(renderer, getEffectiveReaderFontId(), orientedMarginLeft, contentTop, effectiveForceLoad);
   renderStatusBar();
   if (showTruncatedSectionHintThisRender) {
     const int hintX = orientedMarginLeft + 4;
@@ -1912,7 +1923,7 @@ void EpubReaderActivity::renderContents(std::unique_ptr<Page> page, const int or
 
       // Re-render page content to restore images into the blanked area
       // Status bar is not re-rendered here to avoid reading stale dynamic values (e.g. battery %)
-      page->render(renderer, getEffectiveReaderFontId(), orientedMarginLeft, contentTop);
+      page->render(renderer, getEffectiveReaderFontId(), orientedMarginLeft, contentTop, effectiveForceLoad);
       renderer.displayBuffer(HalDisplay::FAST_REFRESH);
     } else {
       renderer.displayBuffer(HalDisplay::HALF_REFRESH);
@@ -1970,7 +1981,10 @@ void EpubReaderActivity::renderContents(std::unique_ptr<Page> page, const int or
     LOG_INF("ERS", "Skipping grayscale/BW-restore for this page (insufficient heap for BW snapshot)");
   }
 
-  if (page->hasImages() && getEffectiveImageRendering() != CrossPointSettings::IMAGES_SUPPRESS) {
+  // Only schedule the half-refresh if real images were decoded on this page.
+  // Placeholder-only pages don't deposit grayscale data that needs settling.
+  if (page->hasImages() && !pageHasPlaceholders &&
+      getEffectiveImageRendering() != CrossPointSettings::IMAGES_SUPPRESS) {
     pendingHalfRefreshAfterImagePage = true;
   }
 

src/activities/reader/EpubReaderActivity.h

@@ -109,6 +109,11 @@ class EpubReaderActivity final : public Activity {
   unsigned long lastPageTurnTime = 0UL;
   unsigned long pageTurnDuration = 0UL;
   bool pendingHalfRefreshAfterImagePage = false;
+  // When true, large images on the current page are decoded instead of shown as placeholders.
+  // Reset to false on every page turn so the next image page starts with a placeholder again.
+  bool forceLoadLargeImages = false;
+  // Set after each render: true if the current page contains at least one placeholder image.
+  bool pageHasPlaceholders = false;
   // Temporary AA suspension when BW snapshot allocation fails under memory pressure.
   // Automatically lifted once heap recovers above hysteresis thresholds.
   bool antiAliasingSuspendedLowMemory = false;