Import of PDF > Previewing Monochrome Bitmaps With VPE

High resolution monochrome bitmaps are difficult to preview on the screen, due to the lower screen-resolution. When scaling an image to a lower resolution, pixels are removed and the result looks frayed - especially with monochrome bitmaps. To overcome this problem, VPE Professional Edition and higher provides the Scale-to-Gray technology. The Scale-to-Gray technology is especially useful for displaying monochrome bitmaps that contain text - like forms - on the screen, because a monochrome image is scaled down to the low screen resolution, while the loss of visual information (the pixels, that are left out) is transformed to gray-values of different intensity (brightness). This produces very good readability for the human eye.

When using this technology, import each bitmap twice. For the preview version, set the property PictureScale2GrayFloat = true and Printable = false. This creates a gray-scale bitmap for the screen. For the bitmap that shall be printed, set the property PictureScale2GrayFloat = false, Viewable = false and Printable = true.

As a result you have two overlayed images on the same page: One is visible in the preview but not printed, and the other is not visible in the preview, but printed (and exported). For details, please see „Scale-to-Gray Technology“ in this manual.

It should be mentioned that changing the zoom factor of the preview causes the Scale-to-Gray image to be recomputed accordingly. The larger the zoom factor, the longer it takes and the bigger is the created Scale-to-Gray image. We recommend to limit the maximum possible zoom factor for the preview to 150% - 200% in this case. To do so, set the property MaxScalePercent =150 (or 200).