I'm puzzled by an example where level adjustments (extreme settings) can lead to the resulting in color saturation go to maximum.
So my first question: When applying color levels (High input < 6) on a layer mask, is it normal that the resulting output colors can become "scrambled" ?
Second question: Layer mask in general - Is it true that the layer mask can only - for each pixel - set a transparency between 0-100? Or is there exceptions from this that I haven't considered?
Because if the above questions have the answers "No" and then "Yes", then it seems I just found a bug in Gimp. Can you have a look at this file (original colors in layers and resulting colors after layer mask) and tell me if this output is normal or if I should file a bug.
Can you post the picture with the mask "before" you piush it?
There are globally three ways to represent channels in Gimp:
As a value in the [0.0 ... 1.0] interval (Pixel in the Pointer and Sample points dialogs). This is mathematically how thing work under the hood in 2.10)
As a percent [0% ... 100%] (RGB(%) in said dialogs), so 100% is the same as 1.0 in Pixel.
As a 8-bit channel value in the [0 ... 255] range (RGB(0..255) in said dialogs) so 255 in the same as 100% in RGB(%) or 1.0 in Pixel.
So your opacity is likely expressed in percent...
To add to the fun the Pixel value is a linear scale, while the RGB values are "perceptual", so a "middle" gray (gray that has the same overall luminosity as a dense checkerboard) is .50 in Pixel, but 73% (RGB(%)) and 186(RGB(0..255))
12-13-2023, 11:53 PM (This post was last modified: 12-13-2023, 11:56 PM by Ofnuts.)
Weird...
If I use your "Before" image, and threshold the mask to 0.06 I get essentially the same mask as in your "impossible colors" picture, but the image looks good.
If I copy/paste that new mask to the mask of the bad picture, the picture is fixed
If I copy the mask of the bad picture and the mask of the good picture as layers in a new picture and compare them... more weirdness ensues. The masks look identical, so putting the top one in Difference mode should give a black image.... and it doesn't. And when I use the Pointer dialog to look at the mask values, these values are completely out of range. The values that should all be 0. <= x <= 1.0 (as they are in the mask if the good picture) are in the thousands range! Also, they appear quite random, and two adjacent pixels have very different values.
So my guess is that due to the out of range values in the mask, the code that computes the final color gets out of range colors and what is displayed is a bit random.
So the next step is: what did you do to the mask? A simple thresholding doesn't produce invalid results.
I don't have the full story of the image. I can see if I can find the source image (or similar) and see if I can make to reproduce the results. If I get this, I can try to describe how to reproduce.
Btw: somehow I'm not receiving any emails notifying of post at this forum, I check once a day normally.
I found the original image of the generator. The problem is I don't manage to reproduce the issue by now.
However, I do have a theory about how this came to be. In order to get to a layer mask that resembles a grayscale copy of the original image, I use selection first, and then create the layer mask from selection. Therefore I suspect that I've forgotten to "select none" before further editing.
This is what I do have by now, not sure if it is useful by now.
Ok - cannot upload new atachment, the xcf files are too large.
(12-15-2023, 07:27 PM)Grobe Wrote: I found the original image of the generator. The problem is I don't manage to reproduce the issue by now.
However, I do have a theory about how this came to be. In order to get to a layer mask that resembles a grayscale copy of the original image, I use selection first, and then create the layer mask from selection. Therefore I suspect that I've forgotten to "select none" before further editing.
This is what I do have by now, not sure if it is useful by now.
Ok - cannot upload new atachment, the xcf files are too large.
You can save the XCF with advanced compression (shrinks to around 1/3 of initial size).. The limit on XCF is 2MB and with the compression this should be enough?
(12-15-2023, 07:27 PM)Grobe Wrote: I found the original image of the generator. The problem is I don't manage to reproduce the issue by now.
However, I do have a theory about how this came to be. In order to get to a layer mask that resembles a grayscale copy of the original image, I use selection first, and then create the layer mask from selection. Therefore I suspect that I've forgotten to "select none" before further editing.
This is what I do have by now, not sure if it is useful by now.
Ok - cannot upload new atachment, the xcf files are too large.
You can save the XCF with advanced compression (shrinks to around 1/3 of initial size).. The limit on XCF is 2MB and with the compression this should be enough?
Ok, so there is a 2MB limit. I've scaled the files down so to fit within that limit.
