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wolszhang  
#1 Posted : Monday, July 3, 2017 12:33:42 PM(UTC)
wolszhang

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I have an indexed bitmap that I need to convert to a black and white (monochrome, not grayscale). How can I apply some custom threshold to it? For example, i want all pixels that are less than some thresholds to be white, others black?
Julia Khoptyan  
#2 Posted : Tuesday, July 4, 2017 2:28:16 AM(UTC)
Julia Khoptyan

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Hi Wolszhang,

You can implement this as follows:
Code:

//Setting desired threshold
int threshold = 170;
Aurigma.GraphicsMill.Bitmap bitmap = new Aurigma.GraphicsMill.Bitmap(@"input.jpg");
for(int i = 0; i < bitmap.Palette.Count; i++)
{
     // RGB-to-brightness calculation taken from https://stackoverflow.com/a/596243
     var brightness = (0.299 * bitmap.Palette[i].R + 0.587 * bitmap.Palette[i].G + 0.114 * bitmap.Palette[i].B);
     if (brightness > threshold)
     {
          bitmap.Palette[i] = Aurigma.GraphicsMill.RgbColor.White;
     }
     else
     {
          bitmap.Palette[i] = Aurigma.GraphicsMill.RgbColor.Black;
     }
}
bitmap.ColorManagement.Convert(PixelFormat.Format1bppIndexed);
bitmap.Save(@"output.tif"); 

Best regards,
Julia

thanks 1 user thanked Julia Khoptyan for this useful post.
wolszhang on 7/5/2017(UTC)
daniel12  
#3 Posted : Saturday, July 29, 2017 1:30:50 AM(UTC)
daniel12

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Hi,
I also indexed bitmap that I need to convert to a black and white and want all pixels that are less than some thresholds to be black.I implemented the code as shown below,but it does not work well.What can I do for this and how can I fix the issue?
Thanks!

Edited by moderator Sunday, July 30, 2017 9:28:19 PM(UTC)  | Reason: no external site links are allowed here!

Andrey Semenov  
#4 Posted : Sunday, July 30, 2017 9:46:15 PM(UTC)
Andrey Semenov

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Hi daniel12,

Please post your code that doesn't work and we will take a look. Could you also add some details on the issue?

Regards,
Andrew

Edited by user Sunday, July 30, 2017 9:47:55 PM(UTC)  | Reason: Not specified

Fedor  
#5 Posted : Monday, July 31, 2017 8:52:41 AM(UTC)
Fedor

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Could you post an image you would like to convert?
Best regards,
Fedor Skvortsov
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