The .NET framework provides rich support for generating and manipulating bitmap images, but it lacks one significant feature that is imperative for image processing -- the ability to modify and then save modified bitonal (i.e., black and white or one-bit per pixel) images. Bitonal images are commonly used in document management and document imaging applications for scanned documents. Bitonal images are most commonly stored in the TIFF (Tagged Image File Format) file format with a CCITT Group IV compression algorithm. The ProblemThe .NET Framework supports loading and displaying bitonal images, but that's where the support ends. All drawing in .NET requires a Graphics object, but a Graphics object cannot be created from a bitonal image. Go ahead and try it now if you don't believe me. I'll wait... Here's some code that demonstrates the issue (assuming Bitonal-In.tif is a bitonal image):Bitmap originalBitmap = new Bitmap(@"Bitonal-In.tif");
Graphics g2 = Graphics.FromImage(originalBitmap); This code will generate an "A Graphics object cannot be created from an image that has an indexed pixel format." exception, thereby thwarting our desire to modify our bitonal image. I know, I couldn't believe it either. Read more: Codeproject
Graphics g2 = Graphics.FromImage(originalBitmap); This code will generate an "A Graphics object cannot be created from an image that has an indexed pixel format." exception, thereby thwarting our desire to modify our bitonal image. I know, I couldn't believe it either. Read more: Codeproject