/// <summary>
/// Load a Bitmap (with transparency) from file (*.bmp or *.png) via file content or Bitmap ctor
/// </summary>
/// <param name="fileName"></param>
/// <param name="highContrast"></param>
/// <returns>The Bitmap with fully transparency if available</returns>
public static Bitmap BitmapFromFile(string fileName, bool highContrast = false)
{
Bitmap bitmap = null;
if (string.IsNullOrEmpty(fileName))
{
throw new ArgumentNullException(nameof(fileName));
}
if (!File.Exists(fileName))
{
throw new ArgumentException("File does not exist", nameof(fileName));
}
byte[] bytes = IsBmpFile(fileName);
if (!highContrast && bytes != null)
{
int offBits = BitConverter.ToInt32(bytes, 10); //normally 54
int width = BitConverter.ToInt32(bytes, 18);
int height = BitConverter.ToInt32(bytes, 22);
int length = BitConverter.ToInt16(bytes, 2) - offBits;
NativeMethods.BitmapCompressionMode compression = (NativeMethods.BitmapCompressionMode)BitConverter.ToUInt32(bytes, 30);
short bitCount = BitConverter.ToInt16(bytes, 28);
//Make some tests if it is a ARGB Bitmap
if (bitCount == 32 && compression == NativeMethods.BitmapCompressionMode.BI_RGB)
{
GCHandle gcH = GCHandle.Alloc(bytes, GCHandleType.Pinned);
IntPtr scan0 = gcH.AddrOfPinnedObject() + offBits;
bitmap = new Bitmap(width, height, 4 * width, PixelFormat.Format32bppArgb, scan0);
if (height > 0)
{
bitmap.RotateFlip(RotateFlipType.RotateNoneFlipY);
}
gcH.Free();
return(bitmap);
}
}
//What shall we do with .png files or .bmp files with smaller formats ?
bitmap = new Bitmap(fileName);
if (!highContrast)
{
if (!(bitmap.PixelFormat == PixelFormat.Format32bppArgb || bitmap.PixelFormat == PixelFormat.Format32bppPArgb))
{
bitmap.MakeTransparent(bitmap.GetPixel(0, 0));
}
else
{
if ((int)bitmap.HorizontalResolution != 96)
{
bitmap.SetResolution(96.0f, 96.0f); //only png bitmaps can have other resolution
}
}
}
return(bitmap);
}
public static Bitmap BitmapFromFile(string fileName, bool highContrast = false)
{
Bitmap bitmap = null;
if (!highContrast && !Path.GetExtension(fileName).Equals(".PNG", StringComparison.OrdinalIgnoreCase))
{
byte[] bytes = File.ReadAllBytes(fileName);
string headerMark = Encoding.ASCII.GetString(bytes, 0, 2);
if (headerMark.Equals("BM"))
{
int offBits = BitConverter.ToInt32(bytes, 10); //normally 54
int width = BitConverter.ToInt32(bytes, 18);
int height = BitConverter.ToInt32(bytes, 22);
int length = BitConverter.ToInt16(bytes, 2) - offBits;
NativeMethods.BitmapCompressionMode compression = (NativeMethods.BitmapCompressionMode)BitConverter.ToUInt32(bytes, 30);
short bitCount = BitConverter.ToInt16(bytes, 28);
//Make some tests if it is a ARGB Bitmap
if (bitCount == 32 && compression == NativeMethods.BitmapCompressionMode.BI_RGB)
{
GCHandle gcH = GCHandle.Alloc(bytes, GCHandleType.Pinned);
IntPtr scan0 = gcH.AddrOfPinnedObject() + offBits;
bitmap = new Bitmap(width, height, 4 * width, PixelFormat.Format32bppArgb, scan0);
if (height > 0)
{
bitmap.RotateFlip(RotateFlipType.RotateNoneFlipY);
}
gcH.Free();
//scan0 is copied to other location, we can test it here
//BitmapData data = bitmap.LockBits(new Rectangle(new Point(), bitmap.Size), ImageLockMode.ReadOnly, PixelFormat.Format32bppArgb);
//IntPtr ptr = data.Scan0;
//bitmap.UnlockBits(data);
return(bitmap);
}
}
}
//What shall we do with .png files or .bmp files with smaller formats ?
bitmap = new Bitmap(fileName);
if (!highContrast)
{
if (!(bitmap.PixelFormat == PixelFormat.Format32bppArgb || bitmap.PixelFormat == PixelFormat.Format32bppPArgb))
{
bitmap.MakeTransparent(bitmap.GetPixel(0, 0));
}
else
{
if ((int)bitmap.HorizontalResolution != 96)
{
bitmap.SetResolution(96.0f, 96.0f); //only png bitmaps can have other resolution
}
}
}
return(bitmap);
}
