Merge pull request #55 from jpirnay/fix-progressivejpg

chore: Include upload changes (including progressive jpg fix)

lib/GfxRenderer/BitmapHelpers.cpp

@@ -107,7 +107,7 @@ uint8_t quantize1bit(int gray, int x, int y) {
   return (gray >= adjustedThreshold) ? 1 : 0;
 }
 
-void createBmpHeader(BmpHeader* bmpHeader, int width, int height) {
+void createBmpHeader(BmpHeader* bmpHeader, int width, int height, BmpRowOrder rowOrder) {
   if (!bmpHeader) return;
 
   // Zero out the memory to ensure no garbage data if called on uninitialized stack memory
@@ -125,15 +125,15 @@ void createBmpHeader(BmpHeader* bmpHeader, int width, int height) {
 
   bmpHeader->infoHeader.biSize = sizeof(bmpHeader->infoHeader);
   bmpHeader->infoHeader.biWidth = width;
-  bmpHeader->infoHeader.biHeight = height;
+  bmpHeader->infoHeader.biHeight = (rowOrder == BmpRowOrder::TopDown) ? -height : height;
   bmpHeader->infoHeader.biPlanes = 1;
   bmpHeader->infoHeader.biBitCount = 1;
   bmpHeader->infoHeader.biCompression = 0;
   bmpHeader->infoHeader.biSizeImage = imageSize;
-  bmpHeader->infoHeader.biXPelsPerMeter = 0;
-  bmpHeader->infoHeader.biYPelsPerMeter = 0;
-  bmpHeader->infoHeader.biClrUsed = 0;
-  bmpHeader->infoHeader.biClrImportant = 0;
+  bmpHeader->infoHeader.biXPelsPerMeter = 2835;  // 72 DPI
+  bmpHeader->infoHeader.biYPelsPerMeter = 2835;  // 72 DPI
+  bmpHeader->infoHeader.biClrUsed = 2;
+  bmpHeader->infoHeader.biClrImportant = 2;
 
   // Color 0 (black)
   bmpHeader->colors[0].rgbBlue = 0;

lib/GfxRenderer/BitmapHelpers.h

@@ -11,8 +11,10 @@ uint8_t quantizeSimple(int gray);
 uint8_t quantize1bit(int gray, int x, int y);
 int adjustPixel(int gray);
 
+enum class BmpRowOrder { BottomUp, TopDown };
+
 // Populates a 1-bit BMP header in the provided memory.
-void createBmpHeader(BmpHeader* bmpHeader, int width, int height);
+void createBmpHeader(BmpHeader* bmpHeader, int width, int height, BmpRowOrder rowOrder);
 
 // 1-bit Atkinson dithering - better quality than noise dithering for thumbnails
 // Error distribution pattern (same as 2-bit but quantizes to 2 levels):

lib/Xtc/Xtc.cpp

@@ -7,6 +7,7 @@
 
 #include "Xtc.h"
 
+#include <Bitmap.h>
 #include <HalStorage.h>
 #include <Logging.h>
 
@@ -175,52 +176,12 @@ bool Xtc::generateCoverBmp() const {
     return false;
   }
 
-  // Write BMP header
-  // BMP file header (14 bytes)
-  const uint32_t rowSize = ((pageInfo.width + 31) / 32) * 4;  // Row size aligned to 4 bytes
-  const uint32_t imageSize = rowSize * pageInfo.height;
-  const uint32_t fileSize = 14 + 40 + 8 + imageSize;  // Header + DIB + palette + data
+  // Write 1-bit BMP header (top-down row order)
+  BmpHeader bmpHeader;
+  createBmpHeader(&bmpHeader, pageInfo.width, pageInfo.height, BmpRowOrder::TopDown);
+  coverBmp.write(reinterpret_cast<const uint8_t*>(&bmpHeader), sizeof(bmpHeader));
 
-  // File header
-  coverBmp.write('B');
-  coverBmp.write('M');
-  coverBmp.write(reinterpret_cast<const uint8_t*>(&fileSize), 4);
-  uint32_t reserved = 0;
-  coverBmp.write(reinterpret_cast<const uint8_t*>(&reserved), 4);
-  uint32_t dataOffset = 14 + 40 + 8;  // 1-bit palette has 2 colors (8 bytes)
-  coverBmp.write(reinterpret_cast<const uint8_t*>(&dataOffset), 4);
-
-  // DIB header (BITMAPINFOHEADER - 40 bytes)
-  uint32_t dibHeaderSize = 40;
-  coverBmp.write(reinterpret_cast<const uint8_t*>(&dibHeaderSize), 4);
-  int32_t width = pageInfo.width;
-  coverBmp.write(reinterpret_cast<const uint8_t*>(&width), 4);
-  int32_t height = -static_cast<int32_t>(pageInfo.height);  // Negative for top-down
-  coverBmp.write(reinterpret_cast<const uint8_t*>(&height), 4);
-  uint16_t planes = 1;
-  coverBmp.write(reinterpret_cast<const uint8_t*>(&planes), 2);
-  uint16_t bitsPerPixel = 1;  // 1-bit monochrome
-  coverBmp.write(reinterpret_cast<const uint8_t*>(&bitsPerPixel), 2);
-  uint32_t compression = 0;  // BI_RGB (no compression)
-  coverBmp.write(reinterpret_cast<const uint8_t*>(&compression), 4);
-  coverBmp.write(reinterpret_cast<const uint8_t*>(&imageSize), 4);
-  int32_t ppmX = 2835;  // 72 DPI
-  coverBmp.write(reinterpret_cast<const uint8_t*>(&ppmX), 4);
-  int32_t ppmY = 2835;
-  coverBmp.write(reinterpret_cast<const uint8_t*>(&ppmY), 4);
-  uint32_t colorsUsed = 2;
-  coverBmp.write(reinterpret_cast<const uint8_t*>(&colorsUsed), 4);
-  uint32_t colorsImportant = 2;
-  coverBmp.write(reinterpret_cast<const uint8_t*>(&colorsImportant), 4);
-
-  // Color palette (2 colors for 1-bit)
-  // XTC 1-bit polarity: 0 = black, 1 = white (standard BMP palette order)
-  // Color 0: Black (text/foreground in XTC)
-  uint8_t black[4] = {0x00, 0x00, 0x00, 0x00};
-  coverBmp.write(black, 4);
-  // Color 1: White (background in XTC)
-  uint8_t white[4] = {0xFF, 0xFF, 0xFF, 0x00};
-  coverBmp.write(white, 4);
+  const uint32_t rowSize = ((pageInfo.width + 31) / 32) * 4;
 
   // Write bitmap data
   // BMP requires 4-byte row alignment
@@ -403,49 +364,12 @@ bool Xtc::generateThumbBmp(int height) const {
     return false;
   }
 
-  // Write 1-bit BMP header for fast home screen rendering
-  const uint32_t rowSize = (thumbWidth + 31) / 32 * 4;  // 1 bit per pixel, aligned to 4 bytes
-  const uint32_t imageSize = rowSize * thumbHeight;
-  const uint32_t fileSize = 14 + 40 + 8 + imageSize;  // 8 bytes for 2-color palette
+  // Write 1-bit BMP header (top-down row order)
+  BmpHeader bmpHeader;
+  createBmpHeader(&bmpHeader, thumbWidth, thumbHeight, BmpRowOrder::TopDown);
+  thumbBmp.write(reinterpret_cast<const uint8_t*>(&bmpHeader), sizeof(bmpHeader));
 
-  // File header
-  thumbBmp.write('B');
-  thumbBmp.write('M');
-  thumbBmp.write(reinterpret_cast<const uint8_t*>(&fileSize), 4);
-  uint32_t reserved = 0;
-  thumbBmp.write(reinterpret_cast<const uint8_t*>(&reserved), 4);
-  uint32_t dataOffset = 14 + 40 + 8;  // 1-bit palette has 2 colors (8 bytes)
-  thumbBmp.write(reinterpret_cast<const uint8_t*>(&dataOffset), 4);
-
-  // DIB header
-  uint32_t dibHeaderSize = 40;
-  thumbBmp.write(reinterpret_cast<const uint8_t*>(&dibHeaderSize), 4);
-  int32_t widthVal = thumbWidth;
-  thumbBmp.write(reinterpret_cast<const uint8_t*>(&widthVal), 4);
-  int32_t heightVal = -static_cast<int32_t>(thumbHeight);  // Negative for top-down
-  thumbBmp.write(reinterpret_cast<const uint8_t*>(&heightVal), 4);
-  uint16_t planes = 1;
-  thumbBmp.write(reinterpret_cast<const uint8_t*>(&planes), 2);
-  uint16_t bitsPerPixel = 1;  // 1-bit for black and white
-  thumbBmp.write(reinterpret_cast<const uint8_t*>(&bitsPerPixel), 2);
-  uint32_t compression = 0;
-  thumbBmp.write(reinterpret_cast<const uint8_t*>(&compression), 4);
-  thumbBmp.write(reinterpret_cast<const uint8_t*>(&imageSize), 4);
-  int32_t ppmX = 2835;
-  thumbBmp.write(reinterpret_cast<const uint8_t*>(&ppmX), 4);
-  int32_t ppmY = 2835;
-  thumbBmp.write(reinterpret_cast<const uint8_t*>(&ppmY), 4);
-  uint32_t colorsUsed = 2;
-  thumbBmp.write(reinterpret_cast<const uint8_t*>(&colorsUsed), 4);
-  uint32_t colorsImportant = 2;
-  thumbBmp.write(reinterpret_cast<const uint8_t*>(&colorsImportant), 4);
-
-  // Color palette (2 colors for 1-bit: black and white)
-  uint8_t palette[8] = {
-      0x00, 0x00, 0x00, 0x00,  // Color 0: Black
-      0xFF, 0xFF, 0xFF, 0x00   // Color 1: White
-  };
-  thumbBmp.write(palette, 8);
+  const uint32_t rowSize = (thumbWidth + 31) / 32 * 4;
 
   // Allocate row buffer for 1-bit output
   uint8_t* rowBuffer = static_cast<uint8_t*>(malloc(rowSize));
@@ -628,4 +552,4 @@ void Xtc::prefetchPages(uint32_t pageIndex) const {
     return;
   }
   parser->prefetchWindow(pageIndex);
-}
+}

lib/ZipFile/ZipFile.cpp

@@ -18,6 +18,28 @@ namespace {
 constexpr uint16_t ZIP_METHOD_STORED = 0;
 constexpr uint16_t ZIP_METHOD_DEFLATED = 8;
 
+// RAII zip: opens the zip if not already open, closes on destruction only if
+// it performed the open.  Removes the wasOpen/close boilerplate from every method.
+class ScopedOpenClose final {
+ public:
+  [[nodiscard]] explicit ScopedOpenClose(ZipFile& zf) : zf(zf), needsClose(!zf.isOpen()) {
+    if (needsClose) ok = zf.open();
+  }
+  ~ScopedOpenClose() {
+    if (needsClose && ok) zf.close();
+  }
+  ScopedOpenClose(const ScopedOpenClose&) = delete;
+  ScopedOpenClose& operator=(const ScopedOpenClose&) = delete;
+  ScopedOpenClose(ScopedOpenClose&&) = delete;
+  ScopedOpenClose& operator=(ScopedOpenClose&&) = delete;
+  explicit operator bool() const { return ok || !needsClose; }
+
+ private:
+  ZipFile& zf;
+  bool needsClose = false;
+  bool ok = true;  // true when zip was already open (no open() call needed)
+};
+
 int zipReadCallback(uzlib_uncomp* uncomp) {
   auto* ctx = reinterpret_cast<ZipInflateCtx*>(uncomp);
   if (ctx->fileRemaining == 0) return -1;
@@ -35,17 +57,10 @@ int zipReadCallback(uzlib_uncomp* uncomp) {
 }  // namespace
 
 bool ZipFile::loadAllFileStatSlims() {
-  const bool wasOpen = isOpen();
-  if (!wasOpen && !open()) {
-    return false;
-  }
+  const ScopedOpenClose zip{*this};
+  if (!zip) return false;
 
-  if (!loadZipDetails()) {
-    if (!wasOpen) {
-      close();
-    }
-    return false;
-  }
+  if (!loadZipDetails()) return false;
 
   file.seek(zipDetails.centralDirOffset);
 
@@ -89,9 +104,6 @@ bool ZipFile::loadAllFileStatSlims() {
   lastCentralDirPos = zipDetails.centralDirOffset;
   lastCentralDirPosValid = true;
 
-  if (!wasOpen) {
-    close();
-  }
   return true;
 }
 
@@ -105,17 +117,10 @@ bool ZipFile::loadFileStatSlim(const char* filename, FileStatSlim* fileStat) {
     return false;
   }
 
-  const bool wasOpen = isOpen();
-  if (!wasOpen && !open()) {
-    return false;
-  }
+  const ScopedOpenClose zip{*this};
+  if (!zip) return false;
 
-  if (!loadZipDetails()) {
-    if (!wasOpen) {
-      close();
-    }
-    return false;
-  }
+  if (!loadZipDetails()) return false;
 
   // Phase 1: Try scanning from cursor position first
   uint32_t startPos = lastCentralDirPosValid ? lastCentralDirPos : zipDetails.centralDirOffset;
@@ -179,17 +184,12 @@ bool ZipFile::loadFileStatSlim(const char* filename, FileStatSlim* fileStat) {
     file.seekCur(m + k);
   }
 
-  if (!wasOpen) {
-    close();
-  }
   return found;
 }
 
 long ZipFile::getDataOffset(const FileStatSlim& fileStat) {
-  const bool wasOpen = isOpen();
-  if (!wasOpen && !open()) {
-    return -1;
-  }
+  const ScopedOpenClose zip{*this};
+  if (!zip) return -1;
 
   constexpr auto localHeaderSize = 30;
 
@@ -198,9 +198,6 @@ long ZipFile::getDataOffset(const FileStatSlim& fileStat) {
 
   file.seek(fileOffset);
   const size_t read = file.read(pLocalHeader, localHeaderSize);
-  if (!wasOpen) {
-    close();
-  }
 
   if (read != localHeaderSize) {
     LOG_ERR("ZIP", "Something went wrong reading the local header");
@@ -223,17 +220,12 @@ bool ZipFile::loadZipDetails() {
     return true;
   }
 
-  const bool wasOpen = isOpen();
-  if (!wasOpen && !open()) {
-    return false;
-  }
+  const ScopedOpenClose zip{*this};
+  if (!zip) return false;
 
   const size_t fileSize = file.size();
   if (fileSize < 22) {
     LOG_ERR("ZIP", "File too small to be a valid zip");
-    if (!wasOpen) {
-      close();
-    }
     return false;  // Minimum EOCD size is 22 bytes
   }
 
@@ -243,9 +235,6 @@ bool ZipFile::loadZipDetails() {
   const auto buffer = static_cast<uint8_t*>(malloc(scanRange));
   if (!buffer) {
     LOG_ERR("ZIP", "Failed to allocate memory for EOCD scan buffer");
-    if (!wasOpen) {
-      close();
-    }
     return false;
   }
 
@@ -265,9 +254,6 @@ bool ZipFile::loadZipDetails() {
   if (foundOffset == -1) {
     LOG_ERR("ZIP", "EOCD signature not found in zip file");
     free(buffer);
-    if (!wasOpen) {
-      close();
-    }
     return false;
   }
 
@@ -280,9 +266,6 @@ bool ZipFile::loadZipDetails() {
   zipDetails.isSet = true;
 
   free(buffer);
-  if (!wasOpen) {
-    close();
-  }
   return true;
 }
 
@@ -317,17 +300,10 @@ int ZipFile::fillUncompressedSizes(std::vector<SizeTarget>& targets, std::vector
     return 0;
   }
 
-  const bool wasOpen = isOpen();
-  if (!wasOpen && !open()) {
-    return 0;
-  }
+  const ScopedOpenClose zip{*this};
+  if (!zip) return 0;
 
-  if (!loadZipDetails()) {
-    if (!wasOpen) {
-      close();
-    }
-    return 0;
-  }
+  if (!loadZipDetails()) return 0;
 
   file.seek(zipDetails.centralDirOffset);
 
@@ -384,34 +360,18 @@ int ZipFile::fillUncompressedSizes(std::vector<SizeTarget>& targets, std::vector
     file.seekCur(m + k);
   }
 
-  if (!wasOpen) {
-    close();
-  }
-
   return matched;
 }
 
 uint8_t* ZipFile::readFileToMemory(const char* filename, size_t* size, const bool trailingNullByte) {
-  const bool wasOpen = isOpen();
-  if (!wasOpen && !open()) {
-    return nullptr;
-  }
+  const ScopedOpenClose zip{*this};
+  if (!zip) return nullptr;
 
   FileStatSlim fileStat = {};
-  if (!loadFileStatSlim(filename, &fileStat)) {
-    if (!wasOpen) {
-      close();
-    }
-    return nullptr;
-  }
+  if (!loadFileStatSlim(filename, &fileStat)) return nullptr;
 
   const long fileOffset = getDataOffset(fileStat);
-  if (fileOffset < 0) {
-    if (!wasOpen) {
-      close();
-    }
-    return nullptr;
-  }
+  if (fileOffset < 0) return nullptr;
 
   file.seek(fileOffset);
 
@@ -421,18 +381,12 @@ uint8_t* ZipFile::readFileToMemory(const char* filename, size_t* size, const boo
   const auto data = static_cast<uint8_t*>(malloc(dataSize));
   if (data == nullptr) {
     LOG_ERR("ZIP", "Failed to allocate memory for output buffer (%zu bytes)", dataSize);
-    if (!wasOpen) {
-      close();
-    }
     return nullptr;
   }
 
   if (fileStat.method == ZIP_METHOD_STORED) {
     // no deflation, just read content
     const size_t dataRead = file.read(data, inflatedDataSize);
-    if (!wasOpen) {
-      close();
-    }
 
     if (dataRead != inflatedDataSize) {
       LOG_ERR("ZIP", "Failed to read data");
@@ -446,16 +400,11 @@ uint8_t* ZipFile::readFileToMemory(const char* filename, size_t* size, const boo
     const auto deflatedData = static_cast<uint8_t*>(malloc(deflatedDataSize));
     if (deflatedData == nullptr) {
       LOG_ERR("ZIP", "Failed to allocate memory for decompression buffer");
-      if (!wasOpen) {
-        close();
-      }
+      free(data);
       return nullptr;
     }
 
     const size_t dataRead = file.read(deflatedData, deflatedDataSize);
-    if (!wasOpen) {
-      close();
-    }
 
     if (dataRead != deflatedDataSize) {
       LOG_ERR("ZIP", "Failed to read data, expected %d got %d", deflatedDataSize, dataRead);
@@ -482,9 +431,7 @@ uint8_t* ZipFile::readFileToMemory(const char* filename, size_t* size, const boo
     // Continue out of block with data set
   } else {
     LOG_ERR("ZIP", "Unsupported compression method");
-    if (!wasOpen) {
-      close();
-    }
+    free(data);
     return nullptr;
   }
 
@@ -494,20 +441,14 @@ uint8_t* ZipFile::readFileToMemory(const char* filename, size_t* size, const boo
 }
 
 bool ZipFile::readFileToStream(const char* filename, Print& out, const size_t chunkSize) {
-  const bool wasOpen = isOpen();
-  if (!wasOpen && !open()) {
-    return false;
-  }
+  const ScopedOpenClose zip{*this};
+  if (!zip) return false;
 
   FileStatSlim fileStat = {};
-  if (!loadFileStatSlim(filename, &fileStat)) {
-    return false;
-  }
+  if (!loadFileStatSlim(filename, &fileStat)) return false;
 
   const long fileOffset = getDataOffset(fileStat);
-  if (fileOffset < 0) {
-    return false;
-  }
+  if (fileOffset < 0) return false;
 
   file.seek(fileOffset);
   const auto deflatedDataSize = fileStat.compressedSize;
@@ -518,9 +459,6 @@ bool ZipFile::readFileToStream(const char* filename, Print& out, const size_t ch
     const auto buffer = static_cast<uint8_t*>(malloc(chunkSize));
     if (!buffer) {
       LOG_ERR("ZIP", "Failed to allocate memory for buffer");
-      if (!wasOpen) {
-        close();
-      }
       return false;
     }
 
@@ -530,19 +468,17 @@ bool ZipFile::readFileToStream(const char* filename, Print& out, const size_t ch
       if (dataRead == 0) {
         LOG_ERR("ZIP", "Could not read more bytes");
         free(buffer);
-        if (!wasOpen) {
-          close();
-        }
         return false;
       }
 
-      out.write(buffer, dataRead);
+      if (out.write(buffer, dataRead) != dataRead) {
+        LOG_ERR("ZIP", "Failed to write all output bytes to stream");
+        free(buffer);
+        return false;
+      }
       remaining -= dataRead;
     }
 
-    if (!wasOpen) {
-      close();
-    }
     free(buffer);
     return true;
   }
@@ -551,9 +487,6 @@ bool ZipFile::readFileToStream(const char* filename, Print& out, const size_t ch
     auto* fileReadBuffer = static_cast<uint8_t*>(malloc(chunkSize));
     if (!fileReadBuffer) {
       LOG_ERR("ZIP", "Failed to allocate memory for zip file read buffer");
-      if (!wasOpen) {
-        close();
-      }
       return false;
     }
 
@@ -561,9 +494,6 @@ bool ZipFile::readFileToStream(const char* filename, Print& out, const size_t ch
     if (!outputBuffer) {
       LOG_ERR("ZIP", "Failed to allocate memory for output buffer");
       free(fileReadBuffer);
-      if (!wasOpen) {
-        close();
-      }
       return false;
     }
 
@@ -577,9 +507,6 @@ bool ZipFile::readFileToStream(const char* filename, Print& out, const size_t ch
       LOG_ERR("ZIP", "Failed to init inflate reader");
       free(outputBuffer);
       free(fileReadBuffer);
-      if (!wasOpen) {
-        close();
-      }
       return false;
     }
     ctx.reader.setReadCallback(zipReadCallback);
@@ -623,18 +550,11 @@ bool ZipFile::readFileToStream(const char* filename, Print& out, const size_t ch
       // InflateStatus::Ok: output buffer full, continue
     }
 
-    if (!wasOpen) {
-      close();
-    }
     free(outputBuffer);
     free(fileReadBuffer);
     return success;  // ctx.reader destructor frees the ring buffer
   }
 
-  if (!wasOpen) {
-    close();
-  }
-
   LOG_ERR("ZIP", "Unsupported compression method");
   return false;
 }

platformio.ini

@@ -53,6 +53,7 @@ extra_scripts =
   pre:scripts/build_html.py
   pre:scripts/gen_i18n.py
   pre:scripts/git_branch.py
+  pre:scripts/patch_jpegdec.py
 
 ; Libraries
 lib_deps =

scripts/patch_jpegdec.py

@@ -0,0 +1,68 @@
+"""
+PlatformIO pre-build script: patch JPEGDEC for MCU_SKIP wild pointer crash.
+
+Problem:
+  JPEGDecodeMCU_P computes pMCU = &sMCUs[iMCU & 0xffffff].  When iMCU is
+  MCU_SKIP (-8), the bitmask produces index 0xFFFFF8 (16 777 208), creating a
+  pointer ~33 MB past the 392-entry sMCUs array.  If the progressive JPEG's
+  first scan includes AC coefficients (iScanEnd > 0), the AC decode loop writes
+  through this wild pointer and crashes with a store-access fault.
+
+  Upstream commit 8628297 guarded the DC coefficient write (pMCU[0]) but not the
+  AC coefficient writes at indices 1-63.
+
+Fix:
+  Redirect pMCU to sMCUs[0] when MCU_SKIP is active.  Writes to sMCUs[1..63]
+  are harmless: for JPEG_SCALE_EIGHTH only sMCUs[0] is read for output, and
+  the DC write at sMCUs[0] is already guarded by the existing `if (iMCU >= 0)`
+  check.
+
+Applied idempotently — safe to run on every build.
+"""
+
+Import("env")
+import os
+
+
+def patch_jpegdec(env):
+    libdeps_dir = os.path.join(env["PROJECT_DIR"], ".pio", "libdeps")
+    if not os.path.isdir(libdeps_dir):
+        return
+    for env_dir in os.listdir(libdeps_dir):
+        jpeg_inl = os.path.join(libdeps_dir, env_dir, "JPEGDEC", "src", "jpeg.inl")
+        if os.path.isfile(jpeg_inl):
+            _apply_mcu_skip_pointer_fix(jpeg_inl)
+
+
+def _apply_mcu_skip_pointer_fix(filepath):
+    MARKER = "// CrossPoint patch: safe pMCU for MCU_SKIP"
+    with open(filepath, "r") as f:
+        content = f.read()
+
+    if MARKER in content:
+        return  # already patched
+
+    # The wild-pointer line in JPEGDecodeMCU_P:
+    OLD = "    signed short *pMCU = &pJPEG->sMCUs[iMCU & 0xffffff];"
+
+    NEW = (
+        "    " + MARKER + "\n"
+        "    signed short *pMCU = (iMCU < 0) ? pJPEG->sMCUs\n"
+        "                                     : &pJPEG->sMCUs[iMCU & 0xffffff];"
+    )
+
+    if OLD not in content:
+        print(
+            "WARNING: JPEGDEC MCU_SKIP pointer patch target not found in %s "
+            "— library may have been updated" % filepath
+        )
+        return
+
+    content = content.replace(OLD, NEW, 1)
+    with open(filepath, "w") as f:
+        f.write(content)
+    print("Patched JPEGDEC: safe pMCU for MCU_SKIP in JPEGDecodeMCU_P: %s" % filepath)
+
+
+# Run immediately at script import time (before compilation).
+patch_jpegdec(env)

src/util/ScreenshotUtil.cpp

@@ -62,7 +62,7 @@ bool ScreenshotUtil::saveFramebufferAsBmp(const char* filename, const uint8_t* f
 
   BmpHeader header;
 
-  createBmpHeader(&header, phyWidth, phyHeight);
+  createBmpHeader(&header, phyWidth, phyHeight, BmpRowOrder::BottomUp);
 
   bool write_error = false;
   if (file.write(reinterpret_cast<uint8_t*>(&header), sizeof(header)) != sizeof(header)) {