Transformation with colorFilter not working correctly

Describe the bug

• use a vector drawable that contains a tint with alpha value (it’s just with what I found this issue, I did not test if this is the necessary)
• tint the image with a solid PorterDuffColorFilter
• the alpha value is not replaced correctly by the tint color

Expected behavior

The image should be tinted correctly - this means the filter should be applied as defined => SRC_IN should replace all existing pixels in the image with the provided color e.g.

To Reproduce

Code:

• test activity with all code: here
• drawable (it’s the default one added via android studio): here

Here’s the main code from the example:

val color = Color.WHITE
val mode = PorterDuff.Mode.SRC_IN
		
// Variant 1
binding.iv1.setImageResource(testImage)
binding.iv1.colorFilter = PorterDuffColorFilter(color, mode)

// Variant 2
binding.iv2.setImageResource(testImage)
binding.iv2.drawable.colorFilter = PorterDuffColorFilter(color, mode)

// Variant 3
binding.iv3.load(testImage) {
	transformations(ColorTintTransformation(color, mode))
}

The ColorTintTransformation class is part of the link above, it’s a simple transformation that does apply the filter on the bitmap with the help of the paint…

Logs/Screenshots

Version

1.0.0

[colinrtwhite]

After investigating with @cemore2048, it looks like Glide is using the application context to load the vector drawable whereas Coil uses the local activity context. This is why Glide loads the VectorDrawable without the tint and Coil loads it with the tint.

Both Glide and Coil then convert the vector drawable into a bitmap to perform the transformation, which bakes any tint into the bitmap. Setting the paint.colorFilter then applies the tint on top of the bitmap. Using setImageResource and colorFilter = doesn’t bake the tint into the bitmap, which is why it’s different.

Ultimately, I think Coil is working as intended in this case since using the application context to load the drawable incorrectly discards the tint and won’t always resolve the correct drawable (for instance, it will be incorrect if using a separate drawable for night mode). To have it work the same as Glide, you can remove the android:tint="?attr/colorControlNormal" from the vector drawable’s XML.

[cemore2048]

@colinrtwhite not as much as I’d like. Did take a look and can reproduce getting it correct in the way anesabml was able to. But haven’t looked into a solution since the inkling here is that there’s still an underlying issue.