Translucency and images with Alpha channel

[tehsphinx]

Describe the bug:

When applying Translucency to an image with an alpha channel, the otherwise transparent part of the image becomes visible. Below example uses one of the default icons to show the effect.

To Reproduce:

Steps to reproduce the behaviour:

1. Run the go code below. go run .

Screenshots:

Note: The background of the icon should not be darkened.

Example code:

package main

import (
	"fyne.io/fyne/v2"
	"fyne.io/fyne/v2/app"
	"fyne.io/fyne/v2/canvas"
	"fyne.io/fyne/v2/container"
	"fyne.io/fyne/v2/theme"
)

func main() {
	a := app.New()

	w := a.NewWindow("Test App")
	image := canvas.NewImageFromResource(theme.ConfirmIcon())
	image.Translucency = 0.5
	w.SetContent(container.NewPadded(image))
	w.Resize(fyne.Size{
		Width:  100,
		Height: 100,
	})

	w.ShowAndRun()
}

Device (please complete the following information):

• MacOS
• Big Sur 11.2.1
• go version go1.16 darwin/amd64
• fyne/v2 2.0.0

[tehsphinx]

Might not be that important...

[AlbinoGeek]

Thank you for bringing this to attention, I wasn't sure if I'd simply done something wrong (could not reproduce cleanly.)

[andydotxyz]

Yes, thanks. We currently support an alpha channel or a translucency value but not both.
This should be fixed.

[junmaqiang]

me too I have this ask

[junmaqiang]

this is bug?

img := canvas.NewImageFromResource(theme.VisibilityOffIcon()) img.FillMode = canvas.ImageFillContain img.SetMinSize(fyne.NewSize(237, 237)) img.Translucency = 0.5

[andydotxyz]

Yes

[hkparker]

Running into this now as well. How difficult would it be to address this?

[andydotxyz]

I think the error is in the GL shader - so not an easy fix as far as I can estimate.
However there is a possibility that it relates to colour models in the SVG rasteriser

[hkparker]

Ah, in this case I was using a PNG, so it wouldn't be in any SVG specific code I expect

[andydotxyz]

Oh it was missing from software renderer (I have fixed that locally) so yes looks like a GL issue

[andydotxyz]

Thanks for the prod. I finally found the solution 🎉

[andydotxyz]

This is landed on develop and in the v2.5.3-rc3 that we are testing