Bug report on Curve Picker

[jalamb]

Bug: The pickers do not pick the correct point in the Curves dialogue

The graphs in the Affinity Curves dialogues input at the bottom and output at the left
Input (bottom) has zero left and 100 right
Output (left) has zero bottom and 100 top

This can be seen in the following:
On a CMYK version of a colour chart I have set two Samplers on the Info panel - the left sampler in the white paper, showing 0,0,0,0; and the right sampler in the pure cyan square showing 100,98,1,3

The curve in diagram 1 shows:
a huge spike on the left at zero, from the white of the paper
zero transformed to 87 (from the flat of the line on the left
100 being unchanged by the point top right of the graph

These are confirmed by the new sampler values, the blue tinge to the white paper, and the unchanged solid cyan square

If I now use the picker and place it in the cyan square, the node created on the graph is bottom left, somewhere around (12,12) in coordinates (second screenshot). First it should clearly be at one end of the line (as the blue square is 100% cyan) and it should be at the right-hand end of the line. Similarly if I reset and use the picker to choose from the white area (with zero cyan) it gives me a node top-right, rather than bottom left.

This error can go unnoticed when selecting a single node because the curve will be symmetrical, so, if, say, the point chosen was 80, then the node would be 20, and the resulting curve when dragged down would be down equally at 80 and 20. However when trying to create an S curve, it falls apart (and wastes a lot of time!)

Software version: Affinity Photo 1.7.0.367, Win 10 Home version 1803 OS build 17134.829, 64bit, Intel Core i7-7700HQ installed RAM 16Gb

 

Edited June 16, 2019 by jalamb
added software versions

[R C-R]

1 hour ago, jalamb said:

On a CMYK version of a colour chart I have set two Samplers on the Info panel - the left sampler in the white paper, showing 0,0,0,0; and the right sampler in the pure cyan square showing 100,98,1,3

Are you sure you have the right screenshot? The sampler on the left is not showing 0,0,0,0.

Also, bug reports should be posted to the appropriate Bug Reporting forum, not here in the Questions one.

[Dan C]

1 hour ago, R C-R said:

bug reports should be posted to the appropriate Bug Reporting forum, not here in the Questions one.

I've moved this thread to it's correct location, our QA team should respond shortly

[jalamb]

Yes, it’s the right screenshot. It already has the curve applied, so the white has changed to 87% cyan.

Thanks, Dan C, I didn’t realise that thread was there.

[Chris B]

Hi jalamb,

I'm not going to pretend we haven't struggled to understand, I guess, correctly what you are trying to do or tell us. We know that you are telling us something but understanding it is another matter.

We've spent a bit of time investigating this and comparing it to what Photoshop does and we are getting varying results between the two apps. If you have an app that can correctly demonstrate this, could you let me know and maybe provide screenshots?

I think you've tried to include as much information as you can but it is maybe too much?

Normally, we prefer a recipe to follow where we get a few steps numbered steps (click here, click that, do this etc.) followed by an 'expected' result, what is 'actually' happening and then 'why' you would expect that.

The file would also really help and if you could provide a video of the whole process that would be fantastic.

I'm sorry this isn't the response you were hoping for after a very long delay in us replying and that it might come across as a big ask from us to want a video but if you are onto something here, I would very much like to get to the bottom of it.