Legacy ImageMagick Discussions Archive

I'm using the command line tools, and I'm trying to do some more cool effects. I looked all over anthony's examples and couldn't find them.

1. Cutout filter (not crop, but the color reduction and image simplification filter) It makes the images look more cartoony, stylized.

2. Newsprint. like comic newsprint effect with the dots for colors.

Thanks for at least looking at the examples first.

No I have not created an example of this yet, but the options are there.
See the undeveloped areas at the bottom of the 'Color' examples page.

The operators you wand are...

-colors # reduce image to this many colors.
However colors picked tend to be midtones rather than
primary or secondary colors.

-map color_table_image
resolor the image to the colors found in the given image.

-posterize reduce colors to just primary and secondary colors allowing the
image to be better printed as a poster or banner.

Oh, wow, I missed the one example that was perfect for what I'm doing.

Color Lookup Tables with small LUT worked real well for cutout.

For the newsprint effect, the posterize doesn't make the droplets. here's an example of what I'm looking for:
http://www.europe.redhat.com/documentat ... sprint.png

Any other tips for acheiving that?

I'm not sure. I think Gimp and Photoshop has from special filters for creating news print like screens.

In IM it would be an artistic filter, and I have not even started to explore all those options (it is a masive set).

anthony wrote:I'm not sure. I think Gimp and Photoshop has from special filters for creating news print like screens.

In IM it would be an artistic filter, and I have not even started to explore all those options (it is a masive set).

Sorry for posting to an old thread -- but what are IM artistic filters? Google doesn't seem to know either. Any pointers?
Thanks,
Luke

dognose wrote:Oh, wow, I missed the one example that was perfect for what I'm doing.

Color Lookup Tables with small LUT worked real well for cutout.

For the newsprint effect, the posterize doesn't make the droplets. here's an example of what I'm looking for:
http://www.europe.redhat.com/documentat ... sprint.png

Any other tips for acheiving that?

This link does not go to your examples, but gives a 404 error.

Can you post an example and explain what you did?

News print screens are actually a form a oderdered dither which about a year ago was expaned by me to allow its use in color images.

See IM Examples, Quantization and Dithering, Ordered Dither.
http://www.imagemagick.org/Usage/quantize/#halftone

You can even create your own threshold dither pattern to generate some special dithering effects.

The only problem with this and something I never considered at the time I was working on was that for a proper half-tone dithering a different offset should be used for the dither threshold map, for each of the three primary colors. Further for CMYK you should have four different offsets for the threshold tile pattern.

I never considered adding any offsets to the dither pattern so the only way to do this would be to 'splice' in an offset into each color channel separately, do the half-tone dither, then remove the offset from each channel. Unfortunately nether -splice nor -roll or any other method is known for offseting just one color channel, separate to the others, except by using -separate to handle each channel as a separate image.

Another method would be to create a separate (rolled) threshold pattern for each channel and dither the channels separately. If developed IM could possibility be modified to include such a pattern.

I have created one example (not great), which will appear in a couple of days at...
http://www.imagemagick.org/Usage/quanti ... one_offset

Hello,

I know it's an old post however I'd be curious to know if anybody has any ideas how the PS cutout filter could be done in IM ? Thanks

best guess, try blurring (-blur) the image and then reducing the colors (-colors)

The previous link has since been updated with better offset printing example.
http://www.imagemagick.org/Usage/quanti ... one_offset

The main criticism to the method is that the screen varies directly with pixel intensity, whcih means at edges the 'dots' are not round. This is why for example the 'eye' of the parrot is so sharp and clear, while flat areas of color show the halftone screen effect.

With true halftone printing, all dots are round but of different sizes. This means fine details are lost due to the resolution of the halftone screen. Techniques for this have also now been explored in other discussions, but not to the point of rotated offset printing.

Examples of this have not been added to IM examples, though essentially it is equivalent to..
Dithering with Symbol Patterns
http://www.imagemagick.org/Usage/quanti ... one_offset
But using an array of 'dot' images. -- no rotation effects applied to separate channels.

NOTE: the dots should still be anti-aliased or even slightly blurred, but all dots should strictly be round.


Really it depends on just how serious or accurate you want the effect!

Hello,

Unfortunately I've tried various methods with different results which were nowhere near the result I get with PS. The following:
seems to help in getting closer to PS result though the colors just don't match up.

-median is a pixel averaging filter tool. and is nothing to do with halftone screens.