Re: [Gimp-user] Pure black n white with smooth curves

[Frank Turk <frank iturk com>]

I think you are doing everything you can to get the colors out or reduced.
I think the major problem you are going to have with this image is original
resolution.  It’s just too jaggy to start with.  But I have an interesting
approach you might try anyway:

1. Scale the image up to 4x in height and width.  Yes: this will distort is
more, but we are going to work on that.
2. Apply the filter set you like best for your original attempts to the
blown up image.  This step is really about taste, not rules, so what you
will like will be different than what I will like.
3. Now apply Filters>Artistic>Oilify... to make a valiant attempt to level
out the jaggies you have in the black lines/areas remaining.
4. If you want to attempt further smoothing, use the Select By Color tool
to select all the black left on your image, and the switch to the Paths
dialog.  Use the “Selection to Path” tool to create traced paths for your
selected black parts.
5. Rescale your image down to the size you want to use it in.  If the
master image is not quite what you think you want, try adding a new layer
and then using your traced path either to trace a new outline of the black
parts, or to make the path a selection and fill that with black.

Let me know how that turns out for you.


On Fri, Apr 27, 2018 at 1:56 AM ociebieda <forums gimpusers com> wrote:

> I am already using gimp for years, not professionally, but I know most
> basics.
> I also already used google to find proper solution, but all tutorials are
> not
> exactly about what I need, so please do not send me links about simple
> black n
> white or greyscale conversions.
>
> What I need is to convert colored image to almost pure black n white
> effect with
> smooth curves.
> I am not talking about greyscale with "desaturate" or 2 color with
> "threshold".
>
> Original image in lossless PNG.
> It has various colors that I want to remove, not making them greyscale.
> https://speedstar.itos.pl/gimp/gimp-original.png
>
> Method 1.
> I use "threshold" with value 160, which is close to what I am looking for,
> but
> the problem is that it makes image pure 2 color, and all curves are not
> smooth,
> making no shades between black and white pixels (use pixel perfect zoom
> withot
> blurring filters if you are not sure what I am talking about).
> https://speedstar.itos.pl/gimp/gimp-threshold_160.png
>
> Method 2.
> I use "desaturate" with "average" setting, make duplicate and set layer
> mode to
> "dodge", which keeps smooth curves and nicely removes most filling colors,
> but
> there are grey fogs that can be noticed on chest, upper leg, and shoe.
> https://speedstar.itos.pl/gimp/gimp-desaturate_average_layer_dodge.png
>
> Method 3.
> I use "desaturate" with "average" setting, increase gamma (not brightness,
> because I do not want to touch black color) with "levels" with value 160,
> increase "contrast" to value 96 (127 makes image 2 color), but I am still
> getting grey fogs slightly on chest and noticeably on upper leg, and also
> some
> lines become too small.
>
> https://speedstar.itos.pl/gimp/gimp-desaturate_average_levels_160_contrast_96.png
>
> Method 4.
> I use "color to alpha" on all colors, make duplicate and set layer mode to
> "dodge", which seems to to have better effect than previous methods, but I
> am
> still getting grey fogs that can be noticed on chest, and if I use another
> duplicate and set layer mode to "dodge", then lines become too small.
> https://speedstar.itos.pl/gimp/gimp-all_colors_alpha_layer_dodge.png
>
> Any ideas?
> Thanks for any suggestions, and please, lets discuss it like intelligent
> adults,
> no useless comments, no childish behaviors.
>
>
> --
> ociebieda (via www.gimpusers.com/forums)
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