There seems to be a problem in GradientBrush

General JUCE discussion
1

I am having problem in using Gradient… I have Checked in 1.46 also…

I created a Color Gradient with both the colour 0.0 opacity…
I added a Color(Any color)…
If this is near to Start Point - it is working fine…
But if that colour position is near to End Point , it is not giving the expected result…

ColourGradient cg(Colours::red.withAlpha((uint8)0), 100, 100,   Colours::red.withAlpha((uint8)0), 100, 150, false); 
cg.addColour(0.99, Colours::red);
GradientBrush gb(cg);
g.setBrush(&gb);
g.fillRect(100, 0, 100, 250);

Where as the following code is working fine…

ColourGradient cg(Colours::red.withAlpha((uint8)0), 100, 100,   Colours::red.withAlpha((uint8)0), 100, 150, false); 
cg.addColour(0.01, Colours::red);
GradientBrush gb(cg);
g.setBrush(&gb);
g.fillRect(100, 0, 100, 250);
2

Interesting - it looks like there’s a little inaccuracy in the gradient code… How about this little tweak in juce_ColourGradient.cpp, line 153:

const int numToDo = ((colours.getUnchecked (j) * (numEntries - 1)) >> 16) - index;

3 
ColourGradient cg(Colours::red.withAlpha((uint8)0), 100, 100, Colours::red.withAlpha((uint8)0), 100, 150, false); 
cg.addColour(0.0, Colours::red);
GradientBrush gb(cg);
g.setBrush(&gb);
g.fillRect(100, 0, 100, 250);

ColourGradient cg(Colours::red.withAlpha((uint8)0), 100, 100, Colours::red.withAlpha((uint8)0), 100, 150, false); cg.addColour(0.0, Colours::red); GradientBrush gb(cg); g.setBrush(&gb); g.fillRect(100, 0, 100, 250); [/quote]

4

Seems to be doing the right thing to me… But it looks like you posted the same bit of code twice there?

5

When the proportion is 0.0 it is filling the region above start also…
But if the proportionate is 1.0 it is not filling the region below it…

I mean the proportion which we’ll give while adding a new color to a ColourGradient…

6

It’s just the sort-order of the three points - if you add a point at 0, it’ll insert it before the first point, but at 1.0 it’ll be before the last one. That’s not incorrect, but I see why it’s confusing.

But rather than messing about with things like this, you could just call clearColours() before adding the points you need - then you’re in full control of what’s going on.