/// <summary>
/// Returns a native Picture object
/// </summary>
/// <param name="autoDispose">Release the image resources once done</param>
/// <returns></returns>
Interop.IStdPicture ComInterfaces._Image.GetPicture(bool autoDispose)
{
Interop.IStdPicture picture = ImgExt.ImageToPictureDisp(_bitmap);
if (autoDispose)
{
_bitmap.Dispose();
}
return(picture);
}
/// <summary>
/// Encodes a bitmap to PNG and writes it to a stream.
/// </summary>
/// <param name="bitmap"></param>
/// <param name="destStream"></param>
/// <returns>Lengths of the encoded data</returns>
public static int WritePNG(Bitmap bitmap, Stream destStream)
{
//encode the bitmap to PNG
MemoryStream buffer = new MemoryStream();
if (bitmap.PixelFormat != PixelFormat.Format24bppRgb)
{
//Converts to a 3 channels RGB bitmmap as ARGB is not unsupported
using (Bitmap tmpBitmap = ImgExt.RemoveAlphaChannel(bitmap)) {
tmpBitmap.Save(buffer, ENCODER_PNG, null);
}
}
else
{
bitmap.Save(buffer, ENCODER_PNG, null);
}
var bytes = buffer.GetBuffer();
//Since a PDF file doesn't support the PNG format, the encoded chunks need
//to be extracted from it.
//PNG chunk: [length 4 bytes BE][type 4 bytes][data of length][CRC 4bytes]
int imageLength = 0;
int offset = 8; //starts reading just after the 8 bytes signature
int offsetBreak = (int)buffer.Position - 8; //max length - min read length in a loop
while (offset < offsetBreak)
{
//read the length on 4 bytes BE
int chunkLength = ReadInt32BE(bytes, offset);
//read the type on 4 bytes
int chunkType = ReadInt32BE(bytes, offset + 4);
if (chunkType == 0x49444154) //if chunkType equals "IDAT"
//Writes the chunk to the stream
{
destStream.Write(bytes, offset + 8, chunkLength);
imageLength += chunkLength;
}
//move to the next chunk
offset += chunkLength + 12;
}
return(imageLength);
}
