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Here is the image with the filter applied, before modifying the curves of the image:

enter image description here

And here is the image after modifying the curves (no matter if the image is rasterized or not):

enter image description here

There are only 3 colors allowed in the multitone filter: buttered, neutral blue and black, so all highlights and shadows are split into 3 ranges, and according to the value one of the 3 colors is mapped to create the multitone image.

Modifying the curves I should be able to modify the distribution of these 3 colors (and that's what happens if I open the same image with the same filter that had its curves modified), but no other colors should ever appear.

But modifying the curves brings in yellow and white.

I suppose this is because the curves are applied to the b/w image + the filter, not only to the b/w image.

How do I apply the curves in Illustrator only to the b/w image?

I also suspect that the image need to be saved with the curves change and the filter re-applied to be able to reflect the changes in the final filtered image: to change the color distribution.

But if that is not the case, then I would like to know how to see the changes live, without saving, while modifying the curve, just like when a multitnone image is created with gradient maps where dragging the highlights / shadows slider the changes of the color distribution of the multitone image can be seen in real time.

SVG filters offer much more flexibility in the workflow (especially for images for the web) than gradient maps because many images can be modified just by modifying one filter.

To resume, there are 2 questions:

  • does the image need to be saved and filter re-applied to see the changes in Illustrator, when modifying the curves? And if yes, why?

  • how do I change the curves only of the image and not also of the filter, while the filter is applied to the image?

  • what actually happened here? were the curves applied to both the image and the SVG filter? i did not save anything after I applied the SVG filter. In my understanding there are 2 factors that can be modified to get the final multitone result:

  • either the mapping range (modify the SVg filter, or the gradient map sliders)

  • or the image curves: shadows and highlights

Because Illustrator does not give me an mapping range slider (for my SVG filter) as gradient maps in PS does for the image, I am forced to change the curves of my image, if I want to use the effect as an SVG filter, to finetune it for the best result, best color distribution.

If someone knows how to tune the mapping range of the filter in real time in Illustrator, here is the filter:

<filter id="yellow_black_blue">

<feColorMatrix color-interpolation-filters="sRGB" type="matrix" values="0.3333 0.3333 0.3333 0 0 0.3333 0.3333 0.3333 0 0 0.3333 0.3333 0.3333 0 0 0 0 0 1 0">
</feColorMatrix>
<feComponentTransfer color-interpolation-filters="sRGB">
<feFuncR tableValues="0.4117647058823529 0.0392156862745098 0.9647058823529412" type="table"></feFuncR>
<feFuncG tableValues="0.7490196078431373 0.054901960784313725 0.8901960784313725" type="table"></feFuncG>
<feFuncB tableValues="0.6039215686274509 0.058823529411764705 0.5803921568627451" type="table"></feFuncB>
</feComponentTransfer>
</filter>

Add after one useless "answer" or actually a guess: It's no use to change the order of the effects in the appearance panel. If I move the curves effect before the SVG filter, there are no changes at all, the image is just like after I applied the filter and before I changed the curves.

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  • How is this different than your previous question regarding the same topic? graphicdesign.stackexchange.com/questions/157994/…
    – Scott
    Commented Sep 25, 2022 at 19:16
  • I would note that "limiting colors" is not something RGB images do. Any "limit" is visual only not a spectrum limitation. One would need either an Indexed image or a Spot color image to actually limit colors - so essentially an Index Mode PNG or GIF, because I don't believe SVG supports Spots (maybe it does and I'm ignorant.)
    – Scott
    Commented Sep 25, 2022 at 19:19
  • The other question is about the real time issue, this is about how to apply the curves only to the image, not to the image + filter, while the filter is applied, because I need to be able to see the changes as I change the curves, just like when you drag the shadows highlights slider in PS when you make this effect with gradient maps. Commented Sep 25, 2022 at 19:29
  • Okay, I will test it with index mode PNG and report back. Commented Sep 25, 2022 at 19:31
  • No, the result is the same in indexed PNG. Commented Sep 25, 2022 at 19:41

1 Answer 1

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does the image need to be saved and filter re-applied to see the changes in >Illustrator, when modifying the curves? And if yes, why?

The SVG filtering standard is not really prefered (Adobe is pretty much ignoring SVG consortium). Only reason it hasn't been dropped from use is that its been done as a standard. Nobody really uses or develops this part of the standard anymore (because it does not really make sense to have vectors that have a fixed pixel size). The preview only manipulates visible pixels so to be fast the effects stack isn't really robust enough to do this.

But adobe does not want to remove it nor update it.

NOTE: the svg filter only makes sense if its last thing in your stack. Otherwise it will bug out. Its not robust enough to understand every possible feature slapped on top of it. Especially third party ones. But you cant expect every effect to work under it.

If you rely on this then good luck to you. It will not get fixed (or at least hasn't been fixed in the last 10 years, the illustrator devteam just does not work this way)

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  • I see. I shouldn't be touching the curves actually. In PhotoShop you can fine tune the exact same multitone effect (the distribution of the 3 colors) by creating a gradient map and putting the black in the middle between the yellow and blue, then move the highlight shadows sliders to change the values to which the 3 colors are mapped. Does anyone know how I do the same in Filtered ( filtered.sourceforge.net ) ? Since there is no feature to modify the mapping range in Illustrator. By the way I generate my filters here: codepen.io/airnan/pen/PWmRMe , (copying from dev tools) Commented Sep 26, 2022 at 19:40
  • I am copying out the generated svg filter from the dev tools on that codepen. Does anyone know if I can change the mapping range (the color distribution) using that codepen? Or is there any other tool to create this effect as svg filter, but be able to fine tune it just like when using gradient maps, meaning setting custom mapping ranges to each color: more blue, less black, more yellow, etc... AND WHERE. by changing the range I can also control where on the picture will be more blue, more yellow, and more black. well, i actually need to change the curves for that but yea... Commented Sep 26, 2022 at 19:41
  • the goal would be custom colored multitone images Commented Sep 26, 2022 at 19:44
  • @ChrisP.Bacon svg cant really do true multitone images since it only understands rgb.
    – joojaa
    Commented Sep 26, 2022 at 20:11
  • it can, it's on this codepen: codepen.io/airnan/pen/PWmRMe you can copy out the generated svg filter from the dev tools, but I posted one in this post too Commented Sep 26, 2022 at 20:16

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