I have a symbol in vectors at raw with around 500px width and 600px height. All strokes were outlined.

Saving it straight from its normal size, this is what I get:


However, if I save it in "Save for web" with 100px height, this is what I get:


See the top part with the yellow helmet? The black shape (aka the outlined stroke) is way bolder than the original size.

Why is this happening?

You can download the AI file here: https://www.dropbox.com/s/33pjfcjupkqdoig/Symbol.ai?dl=0

  • By all rights those lines should not be visible at all. Resize the bitmap with Photoshop for comparison. – Jongware Feb 1 '18 at 18:47
  • What stroke width are you using in the original? Does the stroke width hold that size when the image is reduced or perhaps is not reduced sufficiently for proper contrast change? – fred_dot_u Feb 1 '18 at 18:51
  • @usr2564301 resizing the bitmap maintains the correct lines weight. – coldpumpkin Feb 2 '18 at 7:11
  • @fred_dot_u with stroke (not outlined) the result is the same – coldpumpkin Feb 2 '18 at 7:12
  • "resizing the bitmap maintains the correct lines weight" – that statement is so incredulous that I just had to go and try. No, resizing the bitmap in Photoshop does not maintain line weights. There are no 'line weights' in the bitmap. – Jongware Feb 2 '18 at 9:45

I have looked at your .ai file thinking it was something with stroke scaling, but the problem is actually that you have too much details in that area to scale it properly at such a small size.

The full height of the part on top of the helmet is 23px. If you try to reduce it to 10%, it only leaves 2.3 pixels for that part. It looks bolder because you get an average color between the black of the shapes, their darker beige fill and the yellow-beige of the helmet, which "clogs" the space and makes it looks bolder.

At 50%, you can still see details: enter image description here

At 30%, you can see that it's starting to "clog": enter image description here

At 10% as you're doing it, the whole area is basically filled with dark grey: enter image description here

However, if I delete some of the details within this area like this: enter image description here

Then the area remains open. You can also see that you have only 1 or 2 pixels between the top and bottom of that area:

enter image description here

Which gives a better result:

enter image description here

It will be up to you to determine what detail you want to keep to scale it basically to the size of a postage stamp.

  • Or you could use better fitering, at the cost of image being more blurry. – joojaa Feb 1 '18 at 20:10
  • This is probably the most reliable explanation so far. Anyway I don't understand why it gives preference to black instead of yellow since it's mainly yellow, the black is simply an outline... – coldpumpkin Feb 2 '18 at 7:24
  • Don't see it as a preference; think of it as an average. For the sake of a simple explanation, let's say you have 2 contiguous pixels: one white (0%) and one black (100%). If you resize this to 50%, you'll end up with a single pixel with 50% grey. Another example: let's say you have 8 contiguous pixels: 2 black, 4 white and 2 black. If you resize this to 2 pixels (25%), you'll get 2 pixels at about 50% each. It's just the way resampling in Illustrator and Photoshop work when scaling up or down; it averages contiguous colors to determine what to do with the pixels that are added or removed. – BenoitLussier Feb 2 '18 at 11:24
  • Yea but like... It's basically 90% yellow and 10% black. If I resize in Photoshop, it'll work out just fine, see joojaa answer. I don't know why Illustrator messes it up :\ – coldpumpkin Feb 2 '18 at 17:31

It is perfectly possible to scale that image without much fuss if you use a better filtering algorithms than illustrator gives you as a option. Here ive takes your mage and filtered it with lanczos (with imagemagic) form your original down.

enter image description here

If this is or is not this is better is another thing. Anyway you should design your artwork at with its minimum size in mind.

  • So you exported from illustrator and resized the bitmap using imagemagick? That's probably the solution here, but not exactly what I was expecting. I don't understand why illustrator gives preference to black instead of yellow when exporting bitmap. Designing at minimum size will output the same distorted effect unfortunately... – coldpumpkin Feb 2 '18 at 7:22
  • 2
    @coldpumpkin Because it either takes too few samples (art optimized), has a nonlinear working profile or conflates transparency as alpha ( other aa options, not so much that it priorizes black but the conflation stacks the contribution of foreground elements, since you have many black ones on top). There is really no optimal solution for this, there is just mant many technical details that depend on situation and preference. Also yes designing at lowest level solves this problem as it means less lines so no longer this problem. Scaling a ready made design is not designing it again. – joojaa Feb 2 '18 at 8:14

If your target output size is 100px then make your image 100px before you export it.

When it's sized the same as it will be when exported you'll see what the saved result will look like and can edit it to look good at that size.

When scaling be sure to check "scale strokes and effects".

  • Even if I scale it to 100px (and looks good), when exporting it'll output the same distorted result :\ – coldpumpkin Feb 2 '18 at 7:17
  • Hmm, okay, 100 px looking good, "Save for web" as a .png24 at 100 px, view the results at true size, the size it opens up by default in your image viewer. Looks good? If you zoom in of course you'll see the pixel break up, but exported at size and viewed at size it should look just like it does in your art program. Remember 100 px is about 1.3" on your screen. A big icon size. – Webster Feb 2 '18 at 16:09
  • Still the same. Try it out with the file :P – coldpumpkin Feb 2 '18 at 17:30

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