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Quark Xpress Bugs
TIFF over "background: none"
It's easy to make bitmap, a.k.a. "1-bit" TIFFs transparent - if a given pixel has a value of 1, the pixel gets printed, either overprinting or knocking out through what's behind it; if the pixel has a value of 0, then the image underneath is allowed to show through. |
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1-bit TIFF
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Background image and 1-bit TIFF in a picture box with background: white |
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Background image + 1-bit TIFF, colorized white, in a picture box with background: none |
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| Greyscale images are (almost always) 8-bit images, with 256 possible values for the color. CMYK images are 32 bit: 8 bits each for C,M,Y, & K. RGB images are (almost always) 24 bit: 8 bits each for R, G, and B. Quark allows you make these images transparent too, but it does a really lousy job of it.
If you place a greyscale or CMYK TIFF in a picture box with a background of "none," Quark scans the image to find the first and the last pixels in each row that have a value above 0. All of the pixels with a value of 0 outside these non-zero marker pixels will be labeled "transparent," and what's underneath will be allowed to show through. In Quark 3.3, the low res 72 dpi preview is used to make the decisions about which pixels in your high res image are transparent (!). The end result is nasty square chunks taken out of your TIFF. This is particularly noticeable on diagonals. |
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Original TIFF, changed from 1-bit to greyscale (yes, it looks the same)
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Greyscale TIFF minus chunks |
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Yuck! |
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| In Quark 4, the high resolution image is scanned instead of the 72 dpi preview. Bug's fixed, right? Sort of. If you import a TIFF into Q4, Quark says "aha! I'll help you out by automatically generating a clipping path!" Thanks, Quark, but there are many images where pixels with a value of 0 are supposed to be WHITE, not transparent.
Workaround: The vast majority of images do not need to be transparent. All you have to do is change the background color to something other than "none;" in most cases, "white" will do just fine. If you need an image to be partially transparent, save it as a Photoshop EPS with a clipping path. |
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