How Do You Use "withMultipliedAlpha"?

[clevername27]

How Do You Use "withMultipliedAlpha"? (I've read the docs, but am still unclear.) Thank you.

[d.healey]

No idea, to me it seems to behave no differently than the .withAlpha function. Possibly this function is for use with images that have an alpha channel, but I'm just guessing.

This is from the AI

withMultipliedAlpha is a method of the Colour class in JUCE (a cross-platform C++ library for audio processing and GUI development). It returns a new Colour object that is the same as the original, but with its alpha value multiplied by a given factor.

The alpha value of a Colour object represents its transparency, with a value of 1.0 being fully opaque and a value of 0.0 being fully transparent. Multiplying the alpha value by a factor less than 1.0 will reduce the overall transparency of the colour, while multiplying it by a factor greater than 1.0 will increase the transparency.

But my test project doesn't seem to do anything special compared to withAlpha

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[Christoph Hart]

@d-healey It's pretty self explanatory - that's why ChatGPT managed to answer it correctly...

• withAlpha() sets the alpha value regarding of what alpha value was before, so withAlpha(0x66000000, 0.5) yields 0x80000000
• withMultipliedAlpha() multiplies the existing alpha value, so withMultipliedAlpha(0x66000000, 0.5) yields 0x33000000

[d.healey]

@Christoph-Hart So why doesn't my example do anything interesting?

[clevername27]

@Christoph-Hart said in How Do You Use "withMultipliedAlpha"?:

@d-healey It's pretty self explanatory - that's why ChatGPT managed to answer it correctly...

• withAlpha() sets the alpha value regarding of what alpha value was before, so withAlpha(0x66000000, 0.5) yields 0x80000000
• withMultipliedAlpha() multiplies the existing alpha value, so withMultipliedAlpha(0x66000000, 0.5) yields 0x33000000

What would the syntax be? I'm thinking something like this (but not this):

g.setColour(Colour::withMultipliedAlpha(g.get("itemColour"), 0.5);

[clevername27]

@d-healey I think this is simply one of the Great Mysteries of HISE.

[Christoph Hart]

I know that HISE has a few places of mystery, but this isn't one of them.

You use the Colour class with Colours.withXXX(), the first argument is always a colour and the second a float number that does something with it. This is directly taken from the JUCE API and as self-explanatory as it can get.

So why doesn't my example do anything interesting?

If you change the function to withAlpha, you'll notice that the blue gets 100% alpha, instead of 50% alpha max when the knob is turned up.

[clevername27]

@Christoph-Hart Thank you, Chris.