windowscodecs: Simplify the BMP GetSize code and fix for top-down dibs.

dlls/windowscodecs/bmpdecode.c

@@ -118,36 +118,24 @@ static ULONG WINAPI BmpFrameDecode_Release(IWICBitmapFrameDecode *iface)
     return ref;
 }
 
-static HRESULT BmpHeader_GetSize(BITMAPV5HEADER *bih, UINT *puiWidth, UINT *puiHeight)
-{
-    switch (bih->bV5Size)
-    {
-    case sizeof(BITMAPCOREHEADER):
-    {
-        BITMAPCOREHEADER *bch = (BITMAPCOREHEADER*)bih;
-        *puiWidth = bch->bcWidth;
-        *puiHeight = bch->bcHeight;
-        return S_OK;
-    }
-    case sizeof(BITMAPCOREHEADER2):
-    case sizeof(BITMAPINFOHEADER):
-    case sizeof(BITMAPV4HEADER):
-    case sizeof(BITMAPV5HEADER):
-        *puiWidth = bih->bV5Width;
-        *puiHeight = bih->bV5Height;
-        return S_OK;
-    default:
-        return E_FAIL;
-    }
-}
-
 static HRESULT WINAPI BmpFrameDecode_GetSize(IWICBitmapFrameDecode *iface,
     UINT *puiWidth, UINT *puiHeight)
 {
     BmpFrameDecode *This = (BmpFrameDecode*)iface;
     TRACE("(%p,%p,%p)\n", iface, puiWidth, puiHeight);
 
-    return BmpHeader_GetSize(&This->bih, puiWidth, puiHeight);
+    if (This->bih.bV5Size == sizeof(BITMAPCOREHEADER))
+    {
+        BITMAPCOREHEADER *bch = (BITMAPCOREHEADER*)&This->bih;
+        *puiWidth = bch->bcWidth;
+        *puiHeight = bch->bcHeight;
+    }
+    else
+    {
+        *puiWidth = This->bih.bV5Width;
+        *puiHeight = abs(This->bih.bV5Height);
+    }
+    return S_OK;
 }
 
 static HRESULT WINAPI BmpFrameDecode_GetPixelFormat(IWICBitmapFrameDecode *iface,