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How to add alpha channel to the image and convert that image into png format?

Asked by goldensona
on 30 Dec 2012

Hi i want to combine image with the alpha channel having 100%opacity no color it. and after some processing i have to remove the aplha channel .how to remove it can anyone help me to do.



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2 Answers

Answer by Walter Roberson
on 31 Dec 2012
 Accepted answer
imwrite(RGBarray, filename, 'png', 'Alpha', ones(size(RGBarray,1),size(RGBarray,2)) )

When you imread(), use

[RGBdata, map, alpha] = imread(filename, 'png');

Note: this is specific to PNG files. A couple of other image formats handle Alpha this way, but some of the other image formats handle Alpha in other ways.


Walter Roberson
on 2 Jan 2013

What do you mean by "superimposing" in this situation?

on 2 Jan 2013

for image editing purpose, use superimposing or painting ,if i use photoshop to change it will destroy pixel value

Walter Roberson
on 2 Jan 2013

If you change the RGB array values of the image, then they are changed just like with photoshop.

You can display one image on top of another, but it does not sound like you want to do that.

Answer by Image Analyst
on 31 Dec 2012

I'm not sure exactly what you mean. Do you just want to put stuff in the overlay, like with functions plot(), line(), patch(), annotation(), etc. and be able to turn them on or off? Or do you want to save stuff you put in the overlay, say burned into the image and saved as a disk file with export_fig()? Or do you want to do what Walter suggested?


on 16 Jan 2013

its easy to use alpha channel in photoshop

on 27 Jan 2013

can any one tell about tampering localization capability ?

Walter Roberson
on 28 Jan 2013

Maybe, if it were defined. But it sounds like something that should be analyzed through theory (which is outside the scope of this forum), or else through experimentation.

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