.rgba(false) does not work

Expected Behavior

Expect to save the image without the alpha channel.

Current Behavior

Getting an image byte-wise re-interpretted from RGBA to RGB.

Failure Information (for bugs)

Steps to Reproduce

require('jimp').read('test.png', function (err, image) {
  image.rgba(false).write('out.png');
})

Screenshots In (and expected out): Actual out:

Context

• Jimp Version: 0.6.0
• Operating System: Windows 10
• Node version: 8.11.3

Failure Logs

[tgrajewski]

If you’re saving PNGs, then you can try the colorType() method on the image:

image.colorType(0);  // Grayscale without alpha
image.colorType(2);  // Truecolor without alpha

I’m not Jimp contributor, it’s just a thing that I’ve found out in the docs.

[Axenu]

I think I have found the problem.

It appears that the encoder for PNG files are setting both output AND input alpha channel to image.rgba(). This results in the input being read as RGB instead of RGBA which destroys the output.

The solution should be to change Jimp/packages/type-png/src/index.js:50 from inputHasAlpha: data._rgba to inputHasAlpha: data.bitmap.alpha

I tried to fork it and make the change but one of the tests fail, and I am unable to figure out what the test even does. The important part for me is that the image ends up looking as I expect it to.