Is there a way to get textureSize?

Is there a way to get the texture size from within shader code?

Using textureSize() calls in shader code in ZGE results in blank textures. It seems it's just not implemented. Same with iChannelResolution[], which is understandable given it's assuming an array of textures. But textureSize() seems feasible if it could be implemented or is implemented somehow.

EDIT: A bit of background. I'm working on a dither effect implemented as a shader. It can use ZGE's Img Src texture as a dither pattern but I need to get the texture's size, otherwise the user would need to specify a size, which is inconvenient since the user won't easily know the size or be able to set it appropriately.

In case it helps, the working shader is unlisted on shadertoy:
https://www.shadertoy.com/view/43VGR1