Feature proposal: handling tileable images

[vpenades]

Prerequisites

• I have written a descriptive issue title
• I have verified that I am running the latest version of ImageSharp
• I have verified if the problem exist in both DEBUG and RELEASE mode
• I have searched open and closed issues to ensure it has not already been reported

Description

I was wondering if there's any provision for handling tileable images... I know that brushes are tileable by default, but in most processors, image tiling/wrapping is simply not supported.

For example, let's say I have an image (texture) I know it's tileable, and I want to apply a gaussian blur with radius 5. The current behavior is that processed pixels close to a boundary would not take in account the pixels of the opposite boundary. The resulting image, when tiled, would show a noticeable sharp seam between tile limits.

Tipically when texture/tiling has an enumeration like this:

WrapModes:

• None
• WrapX
• WrapY
• MirrorX
• MirrorY

[antonfirsov]

@vpenades interesting proposal, but really not easy to implement because of the cross-library architectural impact it brings. Might be a candidate feature for 2.0, but with our current focus, I'm afraid it's a bit off the radar, unless someone from the community takes care of it.

But we really want to hear the voice of the users, so anyone else having interest in this, please vote/leave your comments! :)

[JimBobSquarePants]

I'd say it only affects only the convolution based processors so theoretically shouldn't be too big a deal. That said a PR would be most welcome.

[antonfirsov]

It probably also affects drawing.

[JimBobSquarePants]

You reckon? I don't think any of the drawing stuff really cares about edge pixels. I could be wrong though, it's not an area I've looked at in a while.

[tocsoft]

Only thing that could be effected in drawing is the ImageBrush and that already tiles the fill image.

[antonfirsov]

Supporting tiling would mean to me that we need to support "cross boundary" drawing in a way like this:

Black lines represent image the boundary, the green hearth represents a single shape drawn by ImageSharp.Drawing.

I view this as a complex feature set based on managing virtual coordinate systems.

[tocsoft]

no don't think we would need to/should support that scenario. It would be trivial to just draw the shape yourself with applying a transform the make it offset to each side.

[JimBobSquarePants]

Fixed with #2060