Define a RGBa color- transparency

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Simon
Simon on 3 Jul 2014
Answered: deeksha rastogi on 31 Dec 2016
Dear all,
is there a workaround to create, for example, a transparent yellow? Apparently Matlab colormap only works with RGB notations, not RGBa. My idea was: trans_yellow=[1 1 0 0.5] I want to define a transparent color, just changing the alpha value for the whole plot does not work for me.
Thanks!

Answers (4)

deeksha rastogi
deeksha rastogi on 31 Dec 2016
but what are the exact working of alpha matting and please write down its source code in matlab.

Dhanyatha
Dhanyatha on 3 Jul 2014
Edited: Dhanyatha on 3 Jul 2014
Currently, the colormap function does not accept more than 3 arguments. However,you can use the TIFF class in MATLAB to specify the alpha parameter for the image.
Refer to this link for an example on how to create a TIFF object with transparency.
To read RGBA image, you can use readRGBAImage(),readRGBATile() or readRGBAStrip() functions. These functions reads image data as RGB, with associated alpha parameter.

Image Analyst
Image Analyst on 3 Jul 2014
Perhaps - take a look at Steve's blog and see if it's what you want: http://blogs.mathworks.com/steve/2009/02/18/image-overlay-using-transparency/

Rini Varghese
Rini Varghese on 5 Apr 2016
You can modify most object colors with 4 input arguments (RGBa notation) in MATLAB (2015). E.g. rectangle(x,y,w,h,'facecolor',[0 1 0,0.08]) will yield a transparent green box. Hope this helps!

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