Using CMYK plane separation to remove colors from an image

#1 Posted : Friday, February 24, 2017 12:07:52 PM(UTC)

Nick

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This shows how to use the ColorSeparateCommand in conjunction with the AddCommand to drop a specific color from an image. This particular code block shows how the black form can be removed from the image, leaving only a 1-bit image of the colored text. This can subsequently be used to mask out the text or for OCR purposes.

Note the ColorSeparateCommand produces four pages in the output rasterimage, one each for cyan, magenta, yellow, and black, in that order. By removing the last (black) page prior to calling AddCommand, only the CMY planes are added together. This can be modified to keep or drop different combinations of colors. As the ColorSeparateCommand returns planes based on intensity, the resultant images are white-on-black, hence using the InvertCommand to create black-on-white before saving the output.

Here's links to the RasterCommands of interest used here.
ColorSeparateCommand
AddCommand
InvertCommand

Code:


      private static void DoColorPlaneSeparation(string input)
      {
         string outPath = Path.GetDirectoryName(input);
         string outFile = Path.GetFileName(input);

         using (RasterCodecs codecs = new RasterCodecs())
         {
            RasterImage image = codecs.Load(input);
            ColorSeparateCommand csc = new ColorSeparateCommand(ColorSeparateCommandType.Cmyk);

            csc.Run(image);

            csc.DestinationImage.RemovePageAt(4);

            AddCommand ac = new AddCommand(AddCommandType.Add);
            ac.Run(csc.DestinationImage);

            InvertCommand ic = new InvertCommand();
            ic.Run(ac.DestinationImage);

            AutoBinarizeCommand abc = new AutoBinarizeCommand();
            abc.Run(ac.DestinationImage);

            string outputFile = Path.Combine(outPath, "output_" + outFile);
            codecs.Save(ac.DestinationImage, outputFile, image.OriginalFormat, image.BitsPerPixel);
         }
      }

File Attachment(s):

output_label.tif (12kb) downloaded 282 time(s).

File Attachment(s):

label.tif (176kb) downloaded 274 time(s).

Edited by user Friday, June 1, 2018 10:37:51 AM(UTC) | Reason: Updating links to v20

Nick Crook
Developer Support Engineer
LEAD Technologies, Inc.

Notification

Using CMYK plane separation to remove colors from an image - Dropping specific portions of an image programatically based on color


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