Photoshop Question posted in
The official user guide can be found here.

How to draw quality image stroke (border) with Imagemagick or PIL? – Photoshop

I tried to draw image stroke (border) to my png image.
original
ph_res
(*expected 19px stroke layer style result by Photoshop)

and I found helpful script from imagemagick forum. (imagemagick discourse) 

convert source.png -background '#2a7940' -alpha background -channel A -blur 9x11 stroked.png

but my best trial is far from Photoshop result.
im_res

I tried many combinations of Radius*Sigma but it seems the best result from blur trick.. (-blur 9×11 for this one)

Question
* Can I have better image stroke from Imagemagick or PIL or other CLI tools?
* If so, how..?
Thank you so much for reading this question.

Tags:

3

Answers


  1. 0

    This might get you started:

    convert bomb-source.png 
  ( +clone -alpha extract -morphology edge-out disk:19 -fill green -opaque white ) 
  -compose lighten -composite -transparent black result.png

    enter image description here

    The -transparent black at the end is not optimal if your central image contains black so I will think about that some more…

    If you add -write stroke.png after the word disk:19 you will get a new file called stroke.png that shows you what the morphology is doing.

    Login or Signup to reply.
  2. 0

    When you need clean edges on an effect you create with ImageMagick, you can double the size of your input image, run the operations, then resize it back to its original input size. It takes longer to run the operations, but the result can be substantially improved. Here’s an example command…

    convert bomb-source.png -write mpr:in -resize 200% 
   -channel A -morphology dilate disk:38 +channel 
   -fill green -colorize 100 -resize 50% mpr:in -composite result.png

    That command starts by reading the input image and storing a copy in a memory register named "mpr:in".

    Then it resizes the input to 200% and uses "-morphology" to dilate the shape by about 38 pixels. That will work out to about 19 pixels after the image is reduced back to its input size.

    Next it colorizes that new shape to make it green and resizes it 50%, which is back to the original size.

    The command finishes by bringing back that "mpr:in" copy of the original image and compositing it over the modified green piece.

    Increasing the size, working on that, and decreasing it after modifying it is called "super sampling". It’s a common technique that results in smoother edges, but it comes at the cost of speed.

    Edited to add the output image…
    enter image description here

    Login or Signup to reply.
  3. 0

    Here is another way where I use -blur to anti-alias the stroke in ImageMagick.

    Input:

    enter image description here

    Line1 - read input
Line2 - clone it and make it fully opaque green
Line3 - clone the input, extract the alpha channel, dilate it to 19 or 20, then blur by 0x1 to antialias and use -level to remove the inner side of the blur
Line4 - put the dilated alpha into the alpha channel of the green image
Line5 - remove the temporary clones, swap the remaining two images and overlay the original over the green
Line6 - write the output

convert bomb-source.png 
( -clone 0 -alpha off -fill green -colorize 100 ) 
( -clone 0 -alpha extract -morphology dilate disk:20 -blur 0x1 -level 50x100% ) 
( -clone 1,2 -compose copy_opacity -composite ) 
-delete 1,2 +swap -compose over -composite 
result.png

    enter image description here

    If you need more antialiasing, increase the blur to 0x2.

    For ImageMagick 7, replace convert with magick.

    Login or Signup to reply.
Please signup or login to give your own answer.

Back To Top
Search