Using the fillpath method, transparency cannot be set, and regardless of how much transparency is set, the transparency of the filled color is always 1.0
waveformPath.lineTo(width, height);
waveformPath.lineTo(0.0f, height);
waveformPath.closeSubPath();
g.setColour(juce::Colour::fromFloatRGBA(1.0f, 0.0f, 0.0f, 0.5f)); // 半透明红色
g.fillPath(waveformPath);
Could you post a minimum test case that can be built? The following code works completely fine on my computer:
void MainPanel::paint(juce::Graphics &g) {
juce::ignoreUnused(g);
juce::Path path;
const auto bound = getLocalBounds().toFloat();
path.startNewSubPath(bound.getTopLeft());
path.lineTo(bound.getTopRight());
path.lineTo(bound.getBottomRight());
path.closeSubPath();
g.setColour(juce::Colour::fromFloatRGBA(1.0f, 0.0f, 0.0f, 0.5f)); // 半透明红色
g.fillPath(path);
}
juce::Path waveformPath;
waveformPath.startNewSubPath(0.0f, juce::jmap(scopeData[0], 0.0f, 1.0f, height, 0.0f));
for (int i = 1; i < scopeSize; ++i)
{
float x = juce::jmap((float)i, 0.0f, (float)(scopeSize - 1), 0.0f, width);
float y = juce::jmap(scopeData[i], 0.0f, 1.0f, height, 0.0f);
waveformPath.lineTo(x, y);
}
waveformPath.lineTo(width, height);
waveformPath.lineTo(0.0f, height);
waveformPath.closeSubPath();
g.setColour(juce::Colour::fromFloatRGBA(1.0f, 0.0f, 0.0f, 0.5f)); // 半透明红色
g.fillPath(waveformPath);
I am using this method to display spectrograms, and every time I call repaint(), I don’t know if it is related to this. The only problem now is that I cannot display a color with transparency. No matter how I modify it, this color always appears
Here is the complete code
void paint (juce::Graphics& g)
{
for (int i = 1; i < scopeSize; ++i)
{
auto bounds = getLocalBounds().toFloat();
float const width = bounds.getWidth();
float const height = bounds.getHeight();
juce::Path waveformPath;
waveformPath.startNewSubPath(0.0f, juce::jmap(scopeData[0], 0.0f, 1.0f, height, 0.0f));
for (int i = 1; i < scopeSize; ++i)
{
float x = juce::jmap((float)i, 0.0f, (float)(scopeSize - 1), 0.0f, width);
float y = juce::jmap(scopeData[i], 0.0f, 1.0f, height, 0.0f);
waveformPath.lineTo(x, y);
}
waveformPath.lineTo(width, height);
waveformPath.lineTo(0.0f, height);
waveformPath.closeSubPath();
g.setColour(juce::Colour::fromFloatRGBA(1.0f, 0.0f, 0.0f, 0.5f));
g.fillPath(waveformPath);
}
}
@rebbur master ! save me! 
@ zsliu98 master ! save me!
The whole body of your paint() runs in a outer loop of scopeSize iterations.
With every run of that outer loop, you draw your scope at 50% alpha, but you are drawing it scopeSize times, one over the other, and the results comes out as opaque if scopeSize is large enough.
It’s like painting on a wall with a brush over and over again over the same spot, eventually the spot ends up being opaque even if a single pass of the brush were to leave it semi-transparent.
I think you should remove the whole outer loop altogether, probably that was left there by a copy/paste (also because the index i is not used anywhere else aside from the inner loop, which declares its own i anyway which shadows the outer i)
thank you very mush，is solution！！！
