Photoshop automatically optimizing by deleting hidden parts of images?

[Kasper F]

I've had a problem with Photoshop for quite some time that I've never been able to find an answer to.

Photoshop for some reason optimizes images when saving them, as in it deletes hidden parts of an image to save space.

An example:

My layer is a solid color.

My mask is a circle, which is applied to the above layer.

When I save the image and I remove the layer mask transparency, this is the new image.

I've tried saving the image to multiple formats, which doesn't seem to make a difference. PNG, TGA, TIF etc.

Does anyone know if it's possible to disable this "feature" ?

For the people who want to try it themselves, I've attached a PSD file to this topic. Simply open this file and save it as another format. Open the newly saved file and go to Layer > Layer Mask > From Transparency. This will seperate the image and the mask and you should be able to see the difference.

[c.pfaffenbichler]

»Does anyone know if it's possible to disable this "feature" ?«

As fas as I know it cannot be turned off and it is indeed a feature. 

Suppose the Layer Mask is applied not to a Solid Color Layer but to a noisy photographic image – the amount of trash data could seriously affect file-size. 

[Kasper F]

I can see how it is useful for a lot of use cases. But I would much rather that Photoshop didn't make that decision for me.

In game art, a lot of time you end up with textures where you use RGBA as 4 seperate Grayscale images. Which makes optimizations like this highly undesireable, since it removes data I want to use.

[c.pfaffenbichler]

Well, it is still called Photoshop; while it offers a lot of features that exceed the original »purpose« they do often seem to lack in comparisson to those of dedicated software (for example animation). 

Can you circumvent png? Does the software you use to process the images further possibly accept psd?

Maybe you could automate a conversion to a »plain« multi-channel image in another format in Photoshop …