On the road to 3.3

Software G'MIC
#1

Here is a running list of changes done on the G’MIC project since the latest (stable) 3.2.0 release.

New features:

  • [core-321] Optimize evaluation of empty boolean expressions (commit).

  • [math-core-321] New function csqrt() computes the square root of a complex number (commit).

  • [stdlib-321] Add new command line_aa: draws anti-aliased lines in images, using Xiaolin Wu’s line algorithm (commit).

gmic_line_aa

  • [stdlib-321] New command da_freeze allows to freeze several dynamic arrays at the same time (commit).

  • [stdlib-321] New command lof returns the list of specified features (separated by commas) for each selected images (commit). For instance: sp lena,eagle,cat,dog ${"lof [w,h]"} returns 512,512,520,480,600,550,1024,685.

Improvements / Changes:

  • [core-321] Command foreach: Add copymark to resulting image names when +foreach is used (commit).

  • [math-core-321] Add detection of the not operator for faster pre-evaluation of some math expressions.

  • [stdlib-321] Convert commands mode3d, moded3d, double3d, focale3d, specl3d, specs3d (aka m3d, md3d, db3d, f3d, sl3d, ss3d), as well as sphere3d, as custom commands rather than native ones (commit).

  • [stdlib-321] Command sphere3d is now able to generate 3D spherical mesh using three different methods: icosahedron subdivision, cube subdivision and spherical angle discretization.

gmic_000000
gmic_0000001344×556 33.2 KB

Bug fixes:

  • [core-321] Fix command name when empty argument is specified (commit).
1 Like
#2

Bonjour,

Thank you for this new command (line_aa).
Many pixels of the original color are lost with this new command.
It is very visible on a black background.
Is this normal?

‘line_aa’ vs ‘line’ :

line_aa

line

Code used for the test :


test_lines :
512,512,1,3
512,512,1,3
repeat 16
 srand $>
 line. {round(u([w,h,w,h])-1)},1,${-RGB} 
 srand $>
 line_aa.. {round(u([w,h,w,h])-1)},1,${-RGB} 
done
text. "line",20,20,16,1,127,127,127
text.. "line_aa",20,20,16,1,127,127,127
#3

That may be the nature of antialiasing. Perhaps allow smudging as opposed to blurring of corners…?

#4

Sometimes it might be helpful to have

PRERELEASE = $(shell date +%y%m%d%H%M)

in the gmic Makefile, if that is accepted in gmic?

#5

I think the anti-aliasing should apply only on the alpha channel if no alpha has been detected, and apply on color if alpha has been detected.

#6

I don’t understand the question, this is exactly line 181 of the current Makefile.

#7

No no %H %M is added!

#8

Ah I see. What would be the point of adding the hour/minute to the prerelease name?
Manage several prerelease done the same day?
Does it happen that often that we need it?

#9

Yes exactly, as I follow your changes/additions!

#10

@afre

line_aa : A simple analysis is enough to see that the result is very different from what is presented on the page

#11

@samj Now I remember the solution. You divide the alpha by 255 if the Alpha(1) is equal to 255. Then divide the color channel by the alpha ignoring zero (just wish G’MIC has a special case of div which ignores 0), then change the alpha back to normal value. This works if and only if your image has an alpha value.

#12

I wonder what would prevent someone needing it to actually write it as a new command.
This seems pretty straightforward :wink:

Concerning the anti-aliased drawing, it may need some update, I’ve just implemented the algorithm as described in the wikipedia page. Any good improvement is welcome.

#13

It depends heavily on each case what you want to happen, I tend to include specific handling per command. Having said that, here’s what I use in my own local testing when required:

gcd_divnz : skip ${1=};
  l[] is_image_arg=${"is_image_arg $1"} onfail is_image_arg=0 done
  if $is_image_arg pass$1 1 +eq. 0 add. .. rm.. div[^-1] . rm.
  else +eq. 0 add[-2,-1] div[^-1] . rm. noarg fi

It handles either gcd_divnz[-2,-1] or gcd_divnz.. . which is convenient for me.

2 Likes
#14

Anyway, another remark on anti-aliased line.

The classical way of doing anti-aliasing is rendering an image at 200%, then reduce its resolution by half when your rendering is finished.
If you do this for the line drawing over a black background, and you compare with the use of line_aa:

foo :
  256,256,1,3
  512,512,1,3

  repeat 100
    coords:=round(u([w,h,w,h]-1))
    col=${-RGB}
    line_aa.. {[$coords]/2},1,$col
    line. $coords,1,$col
  done
  r2dx. 50%

Then you already see that line_aa (left) artificially adds some thickness to the drawn segments, compared to the standard way of doing anti-aliasing rendering (right).

test
test984×520 377 KB

I’m really not sure at which point you want your drawn line pixels having exactly the specified color.
it seems to be in opposition with making anti-aliased rendering.

#15

Nice discussion here: https://diglib.eg.org/xmlui/bitstream/handle/10.2312/14944/025-032.pdf?sequence=1&isAllowed=y

This part pretty much echoes my thoughts on the matter (manual being what a pixel artist would do - automatic/Superpixelator being their method):

image

PS - Wu’s method is fine but I don’t like its ropey appearance.
PPS - Iterative guided filter or rolling guidance may be a dirty way to solidify the line.

#16

It is a trial to improve the visibility of ‘line_aa’.
The result of the rendering is ‘line_aa_plus_matrice’
The original rendering is ‘line_aa’

line_aa_plus_matrice

line_aa

Code :

test_lines_2 :
512,512,1,3
repeat 16
 srand $>
 line_aa. {round(u([w,h,w,h])-1)},1,${-RGB}
done
(0.2,0,0.2;0,1,0;0.2,0,0.2)
convolve[-2] [-1]
rm.
text. "line_aa_plus_matrice",20,20,16,1,127,127,127

@Reptorian
@garagecoder
Thank you for research and the idea.

1 Like
#17

The Cascading Self-Glitching filter in the Gimp GMIC 3.2.0 (stable) GUI at Testing > Joan Rake > Degradations works fine however in the Windows cli latest stable 3.2.0 I get this error:

‘’’
C:\Users\me>gmic v -99 in.png fx_self_glitching_cascade 5,1,0,50,50,3,3,1,55,55,0,45,45,0.75,3,0,0,0,0,1,0,0,256,1,19,0 o out.png

 [gmic] *** Error in ./fx_self_glitching_cascade/*repeat/*local/(...)/*if/modf/*if/modular_formula/ *** Command 'fill': Function 'if()': Missing argument, in expression 'if(!skip; if(0>3, if(!(0%2) ,calc(a)=mf(a+var3_mod); ,calc(a)=amf(a+var3_mod); ); ,if(0>1, if(!(0%2) ,calc(a)=mf(a*(abs(256)/var3_mod)); ,calc(a)=amf(a*(abs(256)/var3_mod)); ); ,if(!(0%2) ,calc(a)=mf(a); ,calc(a)=amf(a); )'.
 [gmic] Command 'fill' has the following description:

fill (+):
value1,_value2,… |
[image] |
‘formula’

Fill selected images with values read from the specified value list,
existing image
or mathematical expression. Single quotes may be omitted in 'formula'.
(equivalent to shortcut command 'f').

Example:
  [#1] 4,4 fill 1,2,3,4,5,6,7
  [#2] 4,4 (1,2,3,4,5,6,7) fill[-2] [-1]
  [#3] 400,400,1,3 fill "X=x-w/2; Y=y-h/2; R=sqrt(X^2+Y^2); a=atan2(Y,X);
   if(R<=180,255*abs(cos(c+200*(x/w-0.5)*(y/h-0.5))),
   850*(a%(0.1*(c+1))))"

‘’’

In Windows cli Version 3.2.0 (pre-release #221102) it works perfectly well, so somehing broke along the way.

I know there’s a perfectly usable Self-Glitching filter under normal Degradations, however I prefer the multiple x,y positional shifts available in the broken one.

Cheers!

#18

line_aa

@David_Tschumperle

Bonjour,

For information I compared the rendering of line_aa with the program of the page Anti-aliased Line | Xiaolin Wu's algorithm - GeeksforGeeks
The results are identical (attached file : comparaison_Xiaolin-Wu.xcf.bz2).
For me there is too much loss of quality using this algorithm on lines :smiling_face_with_tear:
Merci quand même pour la programmation de cette commande :grinning:
comparaison_Xiaolin-Wu.xcf.bz2 (6.2 KB)

#19

I’ll have a look at it. Modf is my command.

1 Like
#20

line_aa

There may be an error in the Wikipedia code:

There is a very clear difference between the rendering of Wikipedia and line_aa visible on test4_Xiaolin-Wu.xcf.bz2 (Gimp image)
test4_Xiaolin-Wu.xcf.bz2 (92.8 KB)

Code :

test_lines_4 :
Larg=394
784,510,1,3
fill_color 255,255,255
repeat 16
 line_aa. 394,5,$Larg,510,1,0,0,255
 Larg+=21
done