blend modes explanation? unfog/unmist?

[Peter1]

 I do have to unfog/unmist a picture C,  somehow, to get more of its content. (1) and (2) which follow are circumscriptions of it, or attempts at it.

 

(1) Where are the blend modes explained? e.g. as formulas like this one (Ego Eram Reputo, Mai 12, 2021, topic/118210-question-about-blend-modes, comment=583366 )

 

Quote

 

Color Burn increases the contrast in proportion to the color of the lower layer.

 

 

I followed the advice in the help documentation to search the forum for "blend modes", but the search returned "126 pages", where I'm lost.

 

(2) Actually I would need I think, a convex mixing of two layers, to simulate fog/mist,

which is C = a*A + (1-a)*B, where: a in the range 0..1, A the picture, B a fog simulation, C the "fogged" picture.

 

and its inverse to unfog/unmist,

which I would try as A=1/a*C + (1-1/a)*B,  where: 1/a is obviously greater than 1.

 

Thanks.

 

 

 

Edited May 5, 2022 by Peter1
title left as per toe_head2001

[Ego Eram Reputo]

1 hour ago, Peter1 said:

 I do have to unfog/unmist a picture C,  somehow, to get more of its content.

This is desperately difficult to do because the fog is masking the contents. A reverse-blend isn't going to remove the fog.

 

2 hours ago, Peter1 said:

(1) Where are the blend modes explained?

I covered standard blend modes in my book - that's where the quoted formula was originally published. 

 

If you show us the picture (remember: it's a family friendly forum) some clever person might be able to suggest techniques to improve the image.

[MJW]

2 hours ago, Peter1 said:

Actually I would need I think, a convex mixing of two layers, to simulate fog/mist,

which is C = a*A + (1-a)*B, where: a in the range 0..1, A the picture, B a fog simulation, C the "fogged" picture.

 

and its inverse to unfog/unmist,

which I would try as A=1/a*C + (1-1/a)*B,  where: 1/a is obviously greater than 1.

 

The first is the normal, default blending mode for layers. There's no blending mode that does the second. You could get a scaled version of A with the Subtract blending mode: a*A = C - (1-a)*B. You could then adjust the contrast and brightness. Of course, blending with fog will reduce the precision of the image that can be recovered, as the limiting case of a=0 demonstrates.

 

(You might want to correct the typo in the title.)

[Reptillian]

What you're looking for is called 'Dehaze'. There are some dehaze filters in gmic.

[otuncelli]

5 hours ago, Peter1 said:

(1) Where are the blend modes explained? e.g. as formulas like this one (Ego Eram Reputo, Mai 12, 2021, topic/118210-question-about-blend-modes, comment=583366 )

 

There is a great answer here.

https://stackoverflow.com/a/5925219

[Peter1]

On 5/5/2022 at 2:26 AM, Ego Eram Reputo said:

If you show us the picture (remember: it's a family friendly forum) some clever person might be able to suggest techniques to improve the image.

 

I believe I found a good solution. The original is the blue image, taken in the year 1982. The second is a intermediary one I don't recall how I did it, but serving as base for seven variants, the third is the mix of these variants and is good enough, providing depth and color. The artifacts in the sky are from the Sharpen operations.

 

Actually I tried many variants in paint.net using Levels, Auto-Level, Curves+ and Sharpen, and mixed seven promising versions with equal weights 1/7 (opacities 1/7 1/6 1/5 1/4 1/3 1/2 1).

 

I'm curious what an experienced user will result.

 

 

 

Edited May 6, 2022 by Peter1
english language, precision

[Reptillian]

My attempt:

 

G'MIC (Auto-Balance + DCP Dehaze)

 

G

Edited May 6, 2022 by Reptillian