Add cover image display in *Continue Reading* card with framebuffer caching (#200)
## Summary * **What is the goal of this PR?** (e.g., Fixes a bug in the user authentication module, Display the book cover image in the **"Continue Reading"** card on the home screen, with fast navigation using framebuffer caching. * **What changes are included?** - Display book cover image in the "Continue Reading" card on home screen - Load cover from cached BMP (same as sleep screen cover) - Add framebuffer store/restore functions (`copyStoredBwBuffer`, `freeStoredBwBuffer`) for fast navigation after initial render - Fix `drawBitmap` scaling bug: apply scale to offset only, not to base coordinates - Add white text boxes behind title/author/continue reading label for readability on cover - Support both EPUB and XTC file cover images - Increase HomeActivity task stack size from 2048 to 4096 for cover image rendering ## Additional Context * Add any other information that might be helpful for the reviewer (e.g., performance implications, potential risks, specific areas to focus on). - Performance: First render loads cover from SD card (~800ms), subsequent navigation uses cached framebuffer (~instant) - Memory: Framebuffer cache uses ~48KB (6 chunks × 8KB) while on home screen, freed on exit - Fallback: If cover image is not available, falls back to standard text-only display - The `drawBitmap` fix corrects a bug where screenY = (y + offset) scale was incorrectly scaling the base coordinates. Now correctly uses screenY = y + (offset scale)
This commit is contained in:
Eunchurn Park
261
lib/Xtc/Xtc.cpp
261
lib/Xtc/Xtc.cpp
@@ -293,6 +293,267 @@ bool Xtc::generateCoverBmp() const {
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return true;
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}
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std::string Xtc::getThumbBmpPath() const { return cachePath + "/thumb.bmp"; }
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bool Xtc::generateThumbBmp() const {
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// Already generated
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if (SdMan.exists(getThumbBmpPath().c_str())) {
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return true;
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}
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if (!loaded || !parser) {
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Serial.printf("[%lu] [XTC] Cannot generate thumb BMP, file not loaded\n", millis());
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return false;
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}
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if (parser->getPageCount() == 0) {
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Serial.printf("[%lu] [XTC] No pages in XTC file\n", millis());
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return false;
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}
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// Setup cache directory
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setupCacheDir();
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// Get first page info for cover
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xtc::PageInfo pageInfo;
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if (!parser->getPageInfo(0, pageInfo)) {
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Serial.printf("[%lu] [XTC] Failed to get first page info\n", millis());
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return false;
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}
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// Get bit depth
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const uint8_t bitDepth = parser->getBitDepth();
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// Calculate target dimensions for thumbnail (fit within 240x400 Continue Reading card)
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constexpr int THUMB_TARGET_WIDTH = 240;
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constexpr int THUMB_TARGET_HEIGHT = 400;
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// Calculate scale factor
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float scaleX = static_cast<float>(THUMB_TARGET_WIDTH) / pageInfo.width;
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float scaleY = static_cast<float>(THUMB_TARGET_HEIGHT) / pageInfo.height;
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float scale = (scaleX < scaleY) ? scaleX : scaleY;
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// Only scale down, never up
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if (scale >= 1.0f) {
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// Page is already small enough, just use cover.bmp
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// Copy cover.bmp to thumb.bmp
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if (generateCoverBmp()) {
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FsFile src, dst;
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if (SdMan.openFileForRead("XTC", getCoverBmpPath(), src)) {
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if (SdMan.openFileForWrite("XTC", getThumbBmpPath(), dst)) {
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uint8_t buffer[512];
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while (src.available()) {
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size_t bytesRead = src.read(buffer, sizeof(buffer));
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dst.write(buffer, bytesRead);
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}
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dst.close();
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}
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src.close();
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}
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Serial.printf("[%lu] [XTC] Copied cover to thumb (no scaling needed)\n", millis());
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return SdMan.exists(getThumbBmpPath().c_str());
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}
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return false;
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}
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uint16_t thumbWidth = static_cast<uint16_t>(pageInfo.width * scale);
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uint16_t thumbHeight = static_cast<uint16_t>(pageInfo.height * scale);
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Serial.printf("[%lu] [XTC] Generating thumb BMP: %dx%d -> %dx%d (scale: %.3f)\n", millis(), pageInfo.width,
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pageInfo.height, thumbWidth, thumbHeight, scale);
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// Allocate buffer for page data
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size_t bitmapSize;
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if (bitDepth == 2) {
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bitmapSize = ((static_cast<size_t>(pageInfo.width) * pageInfo.height + 7) / 8) * 2;
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} else {
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bitmapSize = ((pageInfo.width + 7) / 8) * pageInfo.height;
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}
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uint8_t* pageBuffer = static_cast<uint8_t*>(malloc(bitmapSize));
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if (!pageBuffer) {
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Serial.printf("[%lu] [XTC] Failed to allocate page buffer (%lu bytes)\n", millis(), bitmapSize);
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return false;
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}
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// Load first page (cover)
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size_t bytesRead = const_cast<xtc::XtcParser*>(parser.get())->loadPage(0, pageBuffer, bitmapSize);
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if (bytesRead == 0) {
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Serial.printf("[%lu] [XTC] Failed to load cover page for thumb\n", millis());
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free(pageBuffer);
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return false;
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}
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// Create thumbnail BMP file - use 1-bit format for fast home screen rendering (no gray passes)
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FsFile thumbBmp;
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if (!SdMan.openFileForWrite("XTC", getThumbBmpPath(), thumbBmp)) {
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Serial.printf("[%lu] [XTC] Failed to create thumb BMP file\n", millis());
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free(pageBuffer);
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return false;
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}
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// Write 1-bit BMP header for fast home screen rendering
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const uint32_t rowSize = (thumbWidth + 31) / 32 * 4; // 1 bit per pixel, aligned to 4 bytes
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const uint32_t imageSize = rowSize * thumbHeight;
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const uint32_t fileSize = 14 + 40 + 8 + imageSize; // 8 bytes for 2-color palette
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// File header
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thumbBmp.write('B');
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thumbBmp.write('M');
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thumbBmp.write(reinterpret_cast<const uint8_t*>(&fileSize), 4);
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uint32_t reserved = 0;
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thumbBmp.write(reinterpret_cast<const uint8_t*>(&reserved), 4);
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uint32_t dataOffset = 14 + 40 + 8; // 1-bit palette has 2 colors (8 bytes)
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thumbBmp.write(reinterpret_cast<const uint8_t*>(&dataOffset), 4);
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// DIB header
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uint32_t dibHeaderSize = 40;
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thumbBmp.write(reinterpret_cast<const uint8_t*>(&dibHeaderSize), 4);
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int32_t widthVal = thumbWidth;
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thumbBmp.write(reinterpret_cast<const uint8_t*>(&widthVal), 4);
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int32_t heightVal = -static_cast<int32_t>(thumbHeight); // Negative for top-down
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thumbBmp.write(reinterpret_cast<const uint8_t*>(&heightVal), 4);
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uint16_t planes = 1;
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thumbBmp.write(reinterpret_cast<const uint8_t*>(&planes), 2);
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uint16_t bitsPerPixel = 1; // 1-bit for black and white
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thumbBmp.write(reinterpret_cast<const uint8_t*>(&bitsPerPixel), 2);
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uint32_t compression = 0;
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thumbBmp.write(reinterpret_cast<const uint8_t*>(&compression), 4);
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thumbBmp.write(reinterpret_cast<const uint8_t*>(&imageSize), 4);
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int32_t ppmX = 2835;
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thumbBmp.write(reinterpret_cast<const uint8_t*>(&ppmX), 4);
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int32_t ppmY = 2835;
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thumbBmp.write(reinterpret_cast<const uint8_t*>(&ppmY), 4);
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uint32_t colorsUsed = 2;
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thumbBmp.write(reinterpret_cast<const uint8_t*>(&colorsUsed), 4);
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uint32_t colorsImportant = 2;
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thumbBmp.write(reinterpret_cast<const uint8_t*>(&colorsImportant), 4);
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// Color palette (2 colors for 1-bit: black and white)
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uint8_t palette[8] = {
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0x00, 0x00, 0x00, 0x00, // Color 0: Black
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0xFF, 0xFF, 0xFF, 0x00 // Color 1: White
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};
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thumbBmp.write(palette, 8);
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// Allocate row buffer for 1-bit output
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uint8_t* rowBuffer = static_cast<uint8_t*>(malloc(rowSize));
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if (!rowBuffer) {
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free(pageBuffer);
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thumbBmp.close();
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return false;
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}
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// Fixed-point scale factor (16.16)
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uint32_t scaleInv_fp = static_cast<uint32_t>(65536.0f / scale);
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// Pre-calculate plane info for 2-bit mode
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const size_t planeSize = (bitDepth == 2) ? ((static_cast<size_t>(pageInfo.width) * pageInfo.height + 7) / 8) : 0;
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const uint8_t* plane1 = (bitDepth == 2) ? pageBuffer : nullptr;
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const uint8_t* plane2 = (bitDepth == 2) ? pageBuffer + planeSize : nullptr;
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const size_t colBytes = (bitDepth == 2) ? ((pageInfo.height + 7) / 8) : 0;
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const size_t srcRowBytes = (bitDepth == 1) ? ((pageInfo.width + 7) / 8) : 0;
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for (uint16_t dstY = 0; dstY < thumbHeight; dstY++) {
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memset(rowBuffer, 0xFF, rowSize); // Start with all white (bit 1)
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// Calculate source Y range with bounds checking
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uint32_t srcYStart = (static_cast<uint32_t>(dstY) * scaleInv_fp) >> 16;
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uint32_t srcYEnd = (static_cast<uint32_t>(dstY + 1) * scaleInv_fp) >> 16;
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if (srcYStart >= pageInfo.height) srcYStart = pageInfo.height - 1;
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if (srcYEnd > pageInfo.height) srcYEnd = pageInfo.height;
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if (srcYEnd <= srcYStart) srcYEnd = srcYStart + 1;
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if (srcYEnd > pageInfo.height) srcYEnd = pageInfo.height;
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for (uint16_t dstX = 0; dstX < thumbWidth; dstX++) {
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// Calculate source X range with bounds checking
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uint32_t srcXStart = (static_cast<uint32_t>(dstX) * scaleInv_fp) >> 16;
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uint32_t srcXEnd = (static_cast<uint32_t>(dstX + 1) * scaleInv_fp) >> 16;
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if (srcXStart >= pageInfo.width) srcXStart = pageInfo.width - 1;
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if (srcXEnd > pageInfo.width) srcXEnd = pageInfo.width;
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if (srcXEnd <= srcXStart) srcXEnd = srcXStart + 1;
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if (srcXEnd > pageInfo.width) srcXEnd = pageInfo.width;
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// Area averaging: sum grayscale values (0-255 range)
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uint32_t graySum = 0;
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uint32_t totalCount = 0;
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for (uint32_t srcY = srcYStart; srcY < srcYEnd && srcY < pageInfo.height; srcY++) {
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for (uint32_t srcX = srcXStart; srcX < srcXEnd && srcX < pageInfo.width; srcX++) {
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uint8_t grayValue = 255; // Default: white
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if (bitDepth == 2) {
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// XTH 2-bit mode: pixel value 0-3
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// Bounds check for column index
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if (srcX < pageInfo.width) {
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const size_t colIndex = pageInfo.width - 1 - srcX;
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const size_t byteInCol = srcY / 8;
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const size_t bitInByte = 7 - (srcY % 8);
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const size_t byteOffset = colIndex * colBytes + byteInCol;
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// Bounds check for buffer access
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if (byteOffset < planeSize) {
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const uint8_t bit1 = (plane1[byteOffset] >> bitInByte) & 1;
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const uint8_t bit2 = (plane2[byteOffset] >> bitInByte) & 1;
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const uint8_t pixelValue = (bit1 << 1) | bit2;
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// Convert 2-bit (0-3) to grayscale: 0=black, 3=white
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// pixelValue: 0=white, 1=light gray, 2=dark gray, 3=black (XTC polarity)
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grayValue = (3 - pixelValue) * 85; // 0->255, 1->170, 2->85, 3->0
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}
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}
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} else {
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// 1-bit mode
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const size_t byteIdx = srcY * srcRowBytes + srcX / 8;
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const size_t bitIdx = 7 - (srcX % 8);
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// Bounds check for buffer access
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if (byteIdx < bitmapSize) {
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const uint8_t pixelBit = (pageBuffer[byteIdx] >> bitIdx) & 1;
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// XTC polarity: 1=black, 0=white
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grayValue = pixelBit ? 0 : 255;
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}
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}
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graySum += grayValue;
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totalCount++;
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}
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}
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// Calculate average grayscale and quantize to 1-bit with noise dithering
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uint8_t avgGray = (totalCount > 0) ? static_cast<uint8_t>(graySum / totalCount) : 255;
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// Hash-based noise dithering for 1-bit output
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uint32_t hash = static_cast<uint32_t>(dstX) * 374761393u + static_cast<uint32_t>(dstY) * 668265263u;
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hash = (hash ^ (hash >> 13)) * 1274126177u;
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const int threshold = static_cast<int>(hash >> 24); // 0-255
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const int adjustedThreshold = 128 + ((threshold - 128) / 2); // Range: 64-192
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// Quantize to 1-bit: 0=black, 1=white
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uint8_t oneBit = (avgGray >= adjustedThreshold) ? 1 : 0;
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// Pack 1-bit value into row buffer (MSB first, 8 pixels per byte)
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const size_t byteIndex = dstX / 8;
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const size_t bitOffset = 7 - (dstX % 8);
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// Bounds check for row buffer access
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if (byteIndex < rowSize) {
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if (oneBit) {
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rowBuffer[byteIndex] |= (1 << bitOffset); // Set bit for white
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} else {
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rowBuffer[byteIndex] &= ~(1 << bitOffset); // Clear bit for black
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}
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}
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}
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// Write row (already padded to 4-byte boundary by rowSize)
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thumbBmp.write(rowBuffer, rowSize);
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}
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free(rowBuffer);
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thumbBmp.close();
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free(pageBuffer);
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Serial.printf("[%lu] [XTC] Generated thumb BMP (%dx%d): %s\n", millis(), thumbWidth, thumbHeight,
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getThumbBmpPath().c_str());
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return true;
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}
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uint32_t Xtc::getPageCount() const {
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if (!loaded || !parser) {
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return 0;
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@@ -62,6 +62,9 @@ class Xtc {
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// Cover image support (for sleep screen)
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std::string getCoverBmpPath() const;
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bool generateCoverBmp() const;
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// Thumbnail support (for Continue Reading card)
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std::string getThumbBmpPath() const;
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bool generateThumbBmp() const;
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// Page access
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uint32_t getPageCount() const;
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