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Image Masks Not Downsampled

Feb 24, 2012 9:14 AM



We have a PDF that we want to reduce the file size.  When we select reduce file size, we get a window that reads "document contained image masks that were not downsampled". What does this mean?  The 20 page document contains a lot of cut and paste images of maps and site plans that were built in PowerPoint and InDesign.  Using Acrobat 9.


What steps do we have to take to correct this so we can reduce the file size?




  • Currently Being Moderated
    Feb 24, 2012 10:09 AM   in reply to Barb111111

    It means that the images have a vector mask controlling which areas are visible (acting as a crop). These aren't affected by a RFS action as the vector data is as small as it can be, but the warning is shown because if the underlying bitmap image is resampled, there may be some issues around the edges of the mask (e.g. if the mask very accurately cuts out a shape from a background, some pixels of the background may appear if the image PPI is reduced).

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