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Step 3: For now, leave the setting to ‘White (full opacity)’ and click on ‘Add’. You will see a white box in the coloured
image layer. Click on it to select it.
Step 4: Now select the brush tool, and click and drag on the coloured background. The mask layer will ensure that
black and white background of the second layer shows through.
Step 5: Use Zoom In to enlarge the image and ‘brush’ the entire background black and white.
Step 6: You should get a colored smiley over the black and white smiley.
3.9 ALPHA CHANNEL
In GIMP, you may give your image transparency by adding an alpha channel. The additional channel instructs the
computer which portions of the image are visible (represented by the channel’s black pixels) and which portions are
opaque (the white pixels in the channel). This can also be referred to as an RGBA picture (red, green, blue, alpha).
Creating an Alpha Channel
Locate the Layers palette in the GIMP window’s lower right corner, then right-click on a blank area and select Add
Alpha Channel from the popup menu. That’s all!
#Communication
#Critical Thinking
Video Session
Scan the QR code or visit the following link to watch the videos:
GIMP- What does “Add Alpha Channel” mean? – tutorial: https://www.youtube.com/watch?v=A9aZdPqs17M
Gimp Lesson 10 | Using Transparency and Alpha Channel: https://www.youtube.com/watch?v=HqOZSkjB0kw
Now, open an image in GIMP and make the background transparent.
After watching the videos, answer the following questions:
1. Why should you not save the image as a JPEG image?
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2. When you include an alpha channel, what happens to the file size?
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304 Touchpad Web Applications-XI

