bitmap alignment issue in linux fixed

source/Bitmap.h

@@ -20,13 +20,33 @@
 
 #include <cstdint>
 
-#define BI_RGB 16 //bitmap value for uncompressed color data
+#define BI_RGB 0 //bitmap value for uncompressed color data
+#define CHAR_BM 19778
 
 
 
+//Padding specific to compiler - must account for padded bfType
+// and little-endian order when overlaying struct on buffer
+typedef struct OverlayBitmapFileHeader {
+  uint16_t bfType = CHAR_BM;  //filetype, must be 'BM'
+  uint8_t bfSize0;
+  uint8_t     bfSize1;
+
+  uint8_t     bfSize2;
+  uint8_t     bfSize3;
+  uint16_t bfReserved1 = 0;
+  
+  uint16_t bfReserved2 = 0;
+  uint8_t     bfOffBits0;
+  uint8_t     bfOffBits1;
+
+  uint8_t     bfOffBits2;
+  uint8_t     bfOffBits3;
+  
+} OverlayBitmapFileHeader;
 
 typedef struct BITMAPFILEHEADER {
-  uint16_t bfType = 19778;  //filetype, must be 'BM' (19778)
+  uint16_t bfType = CHAR_BM;//filetype, must be 'BM'
   uint32_t bfSize;          //size in bytes of bitmap file 
   uint16_t bfReserved1 = 0; //unused, except to keep alignment
   uint16_t bfReserved2 = 0; //unused, except to keep alignment

source/Decoder.cpp

@@ -1081,10 +1081,30 @@ int Decodebitmap(const std::string &fileName) {
     fclose(f); 
     return -1; 
   };
+#ifdef _WIN32
   pbfh=(BITMAPFILEHEADER *)buf;
   pbih=(BITMAPINFOHEADER *)(buf+sizeof(BITMAPFILEHEADER));
-  std::cout << "Size of bmp file header: " << sizeof(*pbfh) << std::endl;
-  std::cout << "Size of bmp info header: " << sizeof(*pbih) << std::endl;
+#elif __linux__
+  //Padding different in GCC, cannot overlay directly
+  //Use smaller types and bitwise ops to get the data
+  OverlayBitmapFileHeader *temp;
+  temp=(OverlayBitmapFileHeader *)buf;
+
+  pbfh = (BITMAPFILEHEADER*)malloc(sizeof(BITMAPFILEHEADER));
+  pbfh->bfType       = temp->bfType;
+  pbfh->bfSize       = temp->bfSize3 << 24;
+  pbfh->bfSize      |= temp->bfSize2 << 16;
+  pbfh->bfSize      |= temp->bfSize1 << 8;
+  pbfh->bfSize      |= temp->bfSize0;
+  pbfh->bfReserved1  = temp->bfReserved1;
+  pbfh->bfReserved2  = temp->bfReserved2;
+  pbfh->bfOffBits    = temp->bfOffBits3 << 24;
+  pbfh->bfOffBits   |= temp->bfOffBits2 << 16;
+  pbfh->bfOffBits   |= temp->bfOffBits1 << 8;
+  pbfh->bfOffBits   |= temp->bfOffBits0;
+  
+  pbih=(BITMAPINFOHEADER *)(buf+sizeof(OverlayBitmapFileHeader));
+#endif
 
     std::cout //<< pbfh << "\n"
          << pbfh -> bfType << ", " << &pbfh -> bfType <<"\n"