Lineargradient is drawn offset from specified positon

Question

I made a hue gradient with a Lineargradient with this code: (I know it could have been made simpler with Color.parseColor but it has to be this way for what I intend to do. I cannot use a drawable either.)

colors = new int[]{ Color.HSVToColor(new float[]{0, 1, 1}),
                    Color.HSVToColor(new float[]{60, 1, 1}), 
                    Color.HSVToColor(new float[]{120, 1, 1}), 
                    Color.HSVToColor(new float[]{180, 1, 1}),
                    Color.HSVToColor(new float[]{240, 1, 1}), 
                    Color.HSVToColor(new float[]{300, 1, 1}), 
                    Color.HSVToColor(new float[]{360, 1, 1}) };
Shader shader = new LinearGradient(0, 0, width, 0, colors, null, Shader.TileMode.CLAMP);
paint.setShader(shader);

Which produces this result with slightly offsetted colors, green area is too small and blue area is too large compared with the expected result.

I checked everything. I tried to use new float[]{0f, 1/6f, 2/6f, 3/6f, 4/6f, 5/6f, 1f} instead of null for the positions argument, same result. This might be a bug too.

Note that this is not a duplicate of this post nor this one. These are about incorrect gradient stops set in code which is not my case. It might be related to this one but I don't see how.

EDIT: Maybe this could be solvable by setting unequal positions to colors, but how can I calculate these exact positions?

Honestly, the only difference between actual and expected seems to be some offset. — natario, Dec 03 '16 at 18:11
That's what I'm trying to solve and it cannot be caused by anything in my code outside the one I provided. — Nicolas, Dec 03 '16 at 19:40
Yes, I see. What if you use 0, 1, 1 as the last color, instead of 360, 1, 1? — natario, Dec 04 '16 at 00:10
@natario Do you want 50 free rep, otherwise it'll just disappear forever after the bounty ends. Just post an answer. — Nicolas, Dec 05 '16 at 21:52
Hehe, very tempting (since I am at 9998 at the moment) but no thanks! Just leave this open for the bounty duration, it might attract some very complete answer that you can award. Then accept your own answer. — natario, Dec 06 '16 at 03:25

Nicolas · Accepted Answer · 2020-09-29T17:52:05.367

I've been working to solve this more than 3 hours in total and well... turns out it was almost nothing. And it was in my code. The worst of it is I added a bounty and solved it 15 minutes later.

I drew the gradient in a view with a certain padding and instead of this

LinearGradient(0, 0, width, 0, colors, null, Shader.TileMode.CLAMP);

I had to do this:

LinearGradient(left, 0, right, 0, colors, null, Shader.TileMode.CLAMP);

Somehow the gradient begins before the padding I added to my view, at (0, 0), which is 10 dip left of my gradient start, causing the offset.

It all makes sense now.

Lineargradient is drawn offset from specified positon

1 Answers1