Impossible to create a custom ImageBitmap and draw it on a canvas

[kirill-grouchnikov]

The code in ImageBitmap.asDesktopBitmap is called in DesktopCanvas.drawImage. This path expects the ImageBitmap to be a very specific - and private! - implementation of the interface, namely DesktopImageBitmap. And that implementation can only be used with org.jetbrains.skija.Bitmap class.

How can a desktop Compose app create its own ImageBitmap as a dynamically generated entity? Specifically, I'm looking to port some code that generates noise-based texture at runtime based on certain parameters. That code populates an IntArray where every entry packs ARGB channels of the specific pixel. Then I have a custom implementation of the ImageBitmap interface (much as DesktopImageBitmap is) that returns the relevant subset of the pixels in readPixels. But that implementation of the Compose interface is not accepted at runtime by the DesktopCanvas.drawImage.

[kirill-grouchnikov]

The full stacktrace that starts in DrawScope.drawImage:

Exception in thread "AWT-EventQueue-0 @coroutine#1" java.lang.UnsupportedOperationException: Unable to obtain org.jetbrains.skija.Image
	at androidx.compose.ui.graphics.DesktopImageAssetKt.asDesktopBitmap(DesktopImageAsset.kt:92)
	at androidx.compose.ui.graphics.DesktopCanvas.drawImage-uwcbMjI(DesktopCanvas.kt:167)
	at androidx.compose.ui.graphics.drawscope.CanvasDrawScope.drawImage-JUiai_k(CanvasDrawScope.kt:202)
	at androidx.compose.ui.node.LayoutNodeDrawScope.drawImage-JUiai_k(LayoutNode.kt:1426)
	at androidx.compose.ui.graphics.drawscope.DrawScope$DefaultImpls.drawImage-JUiai_k$default(DrawScope.kt:429)

[olonho]

Isn't it a dup of https://github.com/JetBrains/compose-jb/issues/111?

[kirill-grouchnikov]

This one is different. See https://issuetracker.google.com/issues/173490304 which was filed on Compose as well.

Right now I can "reach" into the backing array of ints / bytes like this:

        val result = ImageBitmap(width = width, height = height)
        val skijaBitmap = result.asDesktopBitmap()
        skijaBitmap.installPixels(
            ImageInfo.makeS32(width, height, ColorAlphaType.UNPREMUL),
            byteDstBuffer, 4L * width
        )

But it's not a cross-platform / compose "pure" solution

[okushnikov]

Please check the following ticket on YouTrack for follow-ups to this issue. GitHub issues will be closed in the coming weeks.