Add reference perspective overlay to Icon-O-Matic.

[jstressman]

I might be helpful to add the option to toggle a reference layer that shows the default perspective as illustrated in the Icon Guidelines: ​https://www.haiku-os.org/development/icon-guidelines

This way we could more easily ensure that we're at least staying close to a standard perspective (and thus hopefully avoid issues like #8747 in the future).

This could be toggled on and off, possibly have its opacity easily altered, and be able to choose whether or not to be shown above or below the other layers.

I created an icon very close to the "reference" image from the Icon Guidelines, but in doing so it raised another question. As you'll see from the attached image, the top perspectives and even shadow perspectives on the two cubes differ.

While comparing that reference icon to other "official" icons, such as the App_GLDirectMode2 icon, it seems pretty clear to me that the reference image has a higher back-end. The App_VirtualBox icon shares the low back-end with the GL one... but other icons like the App_MediaConverter seem to have an even higher back-end angle than the reference image.

How important is it to stick to the reference angle?

If we do add such an overlay to help us "get it right" in the future, which angle should we go with as the default? The slightly higher top/back of the reference one with less perspective on its shadow... or the slightly increased perspective look of the GL / VirtualBox cube icons (with the lower top/back and the shadow that's slightly thicker up front and narrower in the back)?

[jstressman]

overlay showing the dimensions of the reference image when adjusted to scale in Icon-O-Matic

[jstressman]

screenshot showing the slight perspective differences between the reference image and icons like the App_GLDirectMode2 and App_VirtualBox icons (and other icons like App_MediaConverter go the other way and have less perspective than the reference)

[humdinger]

This would not only be of interest for sticking to the icon guideline. If a user could overlay any image, it'd help when converting bitmap icons.

[leavengood]

The guideline image is actually a bit unrealistic, at least as far as perspective is concerned. The back should recede slightly. The App_GLDirectMode2 icon seems more correct. To "prove this" I tried taking some photos of a Rubik's Cube (an original one from the 80s I got as a kid if anyone cares) with the right perspective and shadow. I did not quite get it right, but nonetheless the following attached image should show that the back line on the top should not be quite so "perfect" as the guidelines image.

Of course the guidelines is meant to be that, a guideline, and not necessarily a perfect representation of the icon perspective. But using the App_GLDirectMode2 icon as a model might be a better guideline to the right isometric perspective.

[leavengood]

Rubik's Cube photo with approximate Haiku icon isometric perspective

[Zardshard]

There was some discussion related to this at ​https://discuss.haiku-os.org/t/gsoc-2023-next-up-add-reference-images-haiku-project/13539/3