Get the gray out.
May 15, 2009 9:44 AM   Subscribe

How do I make an image pure black and white (transparent) in Photoshop or Illustrator so that it is suitable for printing on a shot glass?

My band is ordering shot glasses (from here) emblazoned with our name and a bit of the Boston skyline as a promotional item. This is the graphic -- which contains a fair amount of gray that must be eliminated for it to be printed on glass using only black ink. I'm wondering how best to alter the image in Photoshop or Illustrator so that the only color that shows is pure black with no intermediate grays, while still retaining some of the detail of the original image.
posted by inoculatedcities to Computers & Internet (15 answers total) 8 users marked this as a favorite
I get a busted image there.
posted by Guy_Inamonkeysuit at 9:49 AM on May 15, 2009

Change the mode to bitmap, possibly fiddle with the levels/contrast to get the definition you want.
posted by Juliet Banana at 9:52 AM on May 15, 2009

JB's answer will work, or you can use the posterize filter.
posted by Chris4d at 10:03 AM on May 15, 2009

Best answer: tutorial.
posted by Chris4d at 10:05 AM on May 15, 2009

Response by poster: Here's a working link to the image in question.
posted by inoculatedcities at 10:05 AM on May 15, 2009

Response by poster: Thanks for your help!
posted by inoculatedcities at 10:10 AM on May 15, 2009

You are looking for the threshold command. image>adjustments>threshold, this will leave you with a black and white image, and you can use the slider to get it where you want(unlike the posterize command mentioned above)
posted by travis08 at 10:20 AM on May 15, 2009

Posterization will not eliminate the shades of gray from the image. What you want is a black and white dithered image [either a halftone or a diffusion dither or something like that].

This will convert the shades of gray in your image into patterns of small pure black dots. This is how grayscale images are printed in the newspaper.

Here's a quick-and-dirty conversion of your image into a diffusion-dithered B&W image.
posted by chazlarson at 10:27 AM on May 15, 2009

A quick not about posterizing, it WILL eliminate shades of grey if you tell it to only use 2 levels. The problem is that offers you no control.

Threshold is basically like using posterize set to two levels, but offers a slider to control image a bit.

Either way, I would use the levels command to clean up the image first. This will allow you to remove the gray shit (that used to be sky) from around the buildings. It can be found under the image>adjustment>levels.

Just slide the white arrow in the input levels section from the far right, a little to the left.
posted by travis08 at 10:42 AM on May 15, 2009

Oh, I forgot the teach-a-man-to-fish part.

I opened the original in Photoshop Elements and converted the image to a bitmap. The conversion to bitmap asks how you want to do it [threshold, dither, etc.]. I just chose "diffusion dither" and set the output resolution to 600 dpi.
posted by chazlarson at 10:47 AM on May 15, 2009

I had assumed that the OP wanted to end up with a representation of the original image [gray shit and all] using only black ink.
posted by chazlarson at 10:49 AM on May 15, 2009

Response by poster: All good replies, thanks very much.
posted by inoculatedcities at 10:52 AM on May 15, 2009

Chazlarson, the problem I think he will face doing it by dithering is this is going to be printed on a shot glass, which I am guessing will blow out the dither when printing.

Either way, adjust the levels first, as explained above, so you can be starting with the best image you can. And you definitely don't want to do it they way you currently have marked as best answer.
posted by travis08 at 10:55 AM on May 15, 2009

Okay, here's what I came up with

Make an adjustment layer (threshold) and set the threshold to roughly what you want. Then use the doge and burn tools to tweak the original layer (not the adjustment layer). For instance, couldn't find a threshold that gave me good detail on both the Prudential building and the Hancock tower, so I burnt the edge of the Hancock tower to give it a little more definition.

I also used a gaussian blur to clean up some speckles which make the chazlarson's version unappealing to me. This might still be too detailed to print well - a shot glass is pretty small, and the stripes on the skyscrapers and the CITGO are tiny.

If I wanted to spend more time on it I would go in by hand and touch up the antennae on the skyscrapers, so they are straighter/smoother, and eliminate all the white dots/speckles in below the skyline. It also might be worth burning the edges of that building to the left of the Hancock tower - it doesn't have very good contrast against the sky - or maybe crop it out altogether.

PSD (cs3) document here
posted by aubilenon at 11:22 AM on May 15, 2009 [1 favorite]

aubilenon's is the closest to something that would work, but my guess is this will not look that great on a shot glass. my company sells this stuff and folks are always trying to put crazy detailed artwork on small objects.

if you have a regular laser printer, print out the artwork at the actual size it will be on the item. unless you're printing on the face of a watch or a few other items that use super-duper printing methods, the final product will look at least a little worse than what you see in the printout. if the surface is textured, probably much worse.
posted by snofoam at 2:01 PM on May 15, 2009

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