\pard\tx960\tx1920\tx2880\tx3840\tx4800\tx5760\tx6720\tx7680\tx8640\tx9600\f3\b0\i0\ul0\fs28 Q: I have a PostScript file that prints fine on my NeXT printer, but when I print it on my Laserwriter or another monochrome PostScript printer, all the images come out as grey rectangles. What's going on?\
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A: For certain imaging operations, most notably color image support, the NeXT printer code emits the
\b colorimage
\b0 operator. Since this is not a Red Book PostScript operator, most PostScript printers don't have it. Currently, the only printers that have the
\b colorimage
\b0 operator are color PostScript printers and the NeXT 400 DPI laser printer. The NeXT PostScript prologue also emits some code that will draw a grey rectangle on printers that don't have this operator. \
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When printers are equipped with PostScript Level II software from Adobe, they will all have this operator. For now, print these files on your NeXT printer, or view them on your screen.\
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One other common problem with printing PostScript has to do with transparency using the
\b setalpha, currentalpha
\b0 and
\b alphaimage
\b0 operators. It is an application bug to emit setalpha, alphaimage and currentalpha when printing. Since printers are not equipped with alpha-channel compositing, the printed result will also look different than the onscreen version. When an image containing alpha channel compositing is printed, the alpha channel is replaced by a white background. These operators are not a part of PostScript Level II, so they should only be used for artwork destined for the screen, and not the printer. See NextAnswer postscript.312.\
