Caching options. How does it work?

[mc_peko]

Hi.

How do the caching options under Preferences | Display and Caching work?

1 Merged Image
2 Merged Below Active Layer
3 Merged Group
4 Merged Group Below Active Layer

Default is on for all four.

Also, why is this so very poorly documented?

[LeviFiction]

Essentially caching is a way of speeding up the program by only re-drawing the active layer and portions of the image that need to be redrawn. For example the first of the checkboxes is to cache the full merged image. This looks at the whole image, blend modes, transparency, effects, etc. and produces a single merged view of it and caches that view. Now any time the program needs to re-draw the image (such as when say the crop tool is being resize) PSP isn't re-calculating how all of the layers look before updating the display. "Merged Below Active Layer" caches a version of all of the layers beneath the one you currently have selected. So when you add transparency or manipulate blend modes it only has to work on the merged result of all of the layers beneath the active one instead of re-calculating the every time you make a change. And so on.

PSP9's manual gives a good description of this.

Caching Options

These options allow for faster image redraws after you make changes. By default, they are all marked. Turning these options off will likely slow image redraws.

In the Image group box:

Merged Image - Clear this checkbox to stop saving an image cache of your entire merged image.
Merged Below Active Layer - Clear this checkbox to stop saving an image cache of all the layers below the active one.

Group layers Options

Merged Group - Clear this check box to stop saving an image cache of the merge image for each group.
Merged Below Active Layer - Clear this checkbox to stop saving an image cache of all the group layers below the active one.

[mc_peko]

Thanks! I understand at least partly now. Experimenting a bit with the settings now. Mine were all ticked, as is default. Unticking them is supposed to make PSP slower, not faster, I read. But worth a test or two...

[JoeB]

Thanks! I understand at least partly now. Experimenting a bit with the settings now. Mine were all ticked, as is default. Unticking them is supposed to make PSP slower, not faster, I read. But worth a test or two...

Unticking them should make all subsequent edits and changes you make to an image slower, because every time you make a change PSP will have to "re-remember" every previous change. When ticked, PSP remembers and retains (in cache) each change to the image as it happens, so as you make cumulative changes then PSP won't have to redraw and remember all of the previous changes all over again. Previous changes will be cached (like being kept in memory) so that PSP doesn't have to re-remember the previous changes but only the latest one to add to cache/memory.

I notice that you have over 4tb of disc space. How much of that is free and how much is occupied?

[mc_peko]

That helps too.

There was no apparent difference when I unticked all four boxes. But I've only tried this on one large image as of yet.

Is there any apparent reasons for choosing to not cache?

[LeviFiction]

Lack of resources, fact of the matter is you have a pretty beefy computer. You'd probably need to have several layers and be doing lots of editing using blend modes and transparency before you saw any real differences in speed. And I mean a lot of them. Really force PSP to work hard recalculating everything.

[mc_peko]

Yes.

The image I tested with is huge, 600 DPI, lots of both vector, text, bitmap, etc. Even just correcting a typo takes an hour or so.

[JoeB]

Yes.

The image I tested with is huge, 600 DPI, lots of both vector, text, bitmap, etc. Even just correcting a typo takes an hour or so.

Did you try my suggestion in your other thread about moving the text layer and the layer it is related to out of the layer stack and into the workspace and then working with the text? If so, what was the result?

[hartpaul]

Come on Joe!! Slipping up there. I thought you were going to mention PPI v DPI and also that 72, 300, 600 PPI makes no difference to the size and data.

[JoeB]

Come on Joe!! Slipping up there. I thought you were going to mention PPI v DPI and also that 72, 300, 600 PPI makes no difference to the size and data.

I actually posted exactly that info in the previous thread where he complained about it taking an hour to process a simple text correction, explaining both that DPI was incorrect and that PPI made no difference to image size. And he posted back and did acknowledge that he meant PPI. It seems, however, that he has slipped back into his bad habits again! Maybe this will remind him to get back on track, eh?