Fix 8 bugs: SD 1-bit mode GPIO conflict, PNG file handle leak, audio stack overflow, null terminator, error degradation logic, modulo div-by-zero, upload file validation, screen clear before PNG draw. Improve web UI with progress bar and toast feedback.

sound_picture_app/Display_PNG.cpp

@@ -16,8 +16,8 @@ void * pngOpen(const char *filePath, int32_t *size) {
 }
 
 void pngClose(void *handle) {
-  File Image_file = *((File*)handle);
-  if (Image_file) Image_file.close();
+  File* fp = (File*)handle;
+  if (fp && *fp) fp->close();
 }
 
 int32_t pngRead(PNGFILE *page, uint8_t *buffer, int32_t length) {
@@ -44,6 +44,15 @@ void Search_Images(const char* directory) {
   Image_Count = Folder_retrieval(directory, ".png", Image_Names, 100);
 }
 
+// Fill entire screen with black before drawing a new image
+static void clearScreen() {
+  static uint16_t blackLine[MAX_IMAGE_WIDTH];
+  memset(blackLine, 0, sizeof(blackLine));
+  for (int y = 0; y < LCD_HEIGHT; y++) {
+    LCD_addWindow(0, y, LCD_WIDTH - 1, y, blackLine);
+  }
+}
+
 void Display_Image_By_Path(const char* filePath) {
   printf("Displaying image: %s\r\n", filePath);
   int16_t ret = png.open(filePath, pngOpen, pngClose, pngRead, pngSeek, pngDraw);
@@ -52,6 +61,7 @@ void Display_Image_By_Path(const char* filePath) {
     if (png.getWidth() > MAX_IMAGE_WIDTH) {
       printf("Image is too wide for line buffer!\r\n");
     } else {
+      clearScreen();  // Clear leftovers from previous smaller image
       ret = png.decode(NULL, 0);
       png.close();
     }