I would like to show on my map only the reddish pixels of my raster layer.

Said in another way: I would like to transform my white background into transparent background so I can see my other features.

I have the feeling this is possible using the custom transparence tab in the layer property.

enter image description here

  • Have you tried the transparency tab?
    – underdark
    Commented Nov 24, 2015 at 16:49
  • The transparency tab allows me to see my other features, but the red areas will be less marquant.
    – ZKB
    Commented Nov 24, 2015 at 16:59

2 Answers 2


I found a solution to my problem:

enter image description here

In the transparency tab use the mouse selection tool to add a value from the screen by interactively clicking on a pixel. This will automatically add a new line in the table to the left showing the band characteristics of this pixel. Clicking on apply will then set to transparent all the pixels in the raster with the same pixel value.


enter image description here

See the 'Transparent pixel list' under the Transparency Tab. You could set the ranges for your white pixels in this list and give a 100% transparency.

  • I tried your solution but I can't check the "no data value"...
    – ZKB
    Commented Nov 24, 2015 at 18:02
  • probably because a 'NoDataValue' wasn't defined. Glad you solved it - but I think '255' still isn't treated as a NoDataVal which you may or may not want.
    – koshmaster
    Commented Nov 24, 2015 at 19:41

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