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FAQ: Why do annotations become black or white when realized on 1bpp images?
This topic and its replies were posted before the current version of LEADTOOLS was released and may no longer be applicable.
#1
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Friday, June 18, 2010 10:47:40 AM(UTC)
Groups: Registered, Tech Support, Administrators
Posts: 764
Annotations live in a layer outside of the image. Therefore when using and displaying them you can still have color annotations on top of the black and white image. However, when you go to Realize or permanently burn the annotations onto the image you will often just become black or white and often times with hilite annotations completely invisible.
Since the 1bpp image only has two colors the annotations must get converted to those colors in order to become part of the bitmap data. We use Windows functions under the hood to do this and it just does a simple combination based on the intensity. Therefore dark colors such as blue, red, etc. will become black and light colors like yellow become white. If an annotation has alpha (such as a highlight annotation) it will become either invisible or solid.
The workaround to this is to convert the image to 24bpp, realize the annotations, then convert back to 1bpp in some fashion. Probably the best way to go to black and white is using our Halftone feature. Attached is a small C# application that lets you draw annotations and then realize them either by themselves (which results in large black or white annotations) or to do the halftoning workaround. Draw some annotations and click the Realize button. Then move those annotations, select the checkbox and click Realize again to see the difference.
LEADTOOLS Support
Document
Document SDK Questions
FAQ: Why do annotations become black or white when realized on 1bpp images?
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