Gimp How Do I Makeup A Colored Background?

Text and images Copyright (C) 2002 Seth Burgess and may non be used without permission of the author.

Intention¶

to

This tutorial shows you how you can efficiently replace the background of an prototype with another in GIMP, through the utilise of the color to alpha plug-in. The aim is to testify the advantages of using the color to blastoff plug-in over selection-based techniques. To illustrate this, this tutorial will use the above images as source and destination. This tutorial doesn't accost the complexities of treatment real-world photos in this manner, only does briefly discuss information technology at the stop.

Why Non a Selection¶

The common approach to doing many things in GIMP is to first become a good selection. Notwithstanding, when removing an anti-aliased object from its background is non a proficient thought, equally shown above.

You'll note that each of the iii zoomed in selections above take varying amounts of the dark-green-blue mix selected. When these are filled, nosotros are left with apartment black and slightly blueish-green pixels between them, or no transition to blackness at all.

Compare each with the target image below. The left ane has a bluish border around information technology. This looks somewhat neat, merely not what we're going for. The middle i is shut, but there are some ugly visible pixels nonetheless. You can try getting rid of all the ugly pixels, but then you'll finish upward with something jagged similar on the right.

You tin spend hours trying to find something that will work perfectly, but you won't. Anything short of the rightmost image has some blueish in the pixel, which will stick out. You tin become also far, and blend it back to something close, only this is fourth dimension consuming. Instead, may I suggest the rest of the tutorial?

Step 1¶

The offset stride is to actuate the color to alpha plug-in. Its bill of fare location is Filters -> Colors -> Colour To Alpha, where means to correct click on the image. If its grayed-out, it ways that you lot have an indexed image. If its not there, upgrade your gimp to 1.ii.ten.

Step 2¶

Next utilise the Color Picker Tool to select the background color.

Step 3¶

When you used the color picker to select the background, a window with the colour popped up. Click, hold, and drag from the color portion of this window to the color portion of the Colour To Alpha plug-in. If using Gimp for Windows, you'll accept to right-click on the destination button and select the Foreground - drag northward' driblet doesn't work. Click OK subsequently the color indicator on the Color To Alpha plug-in is changed to bluish.

Step 4¶

There should now be a nice greenish and alpha image with no trace of the blueish left. Side by side add together the new background.

Step 5¶

Now create a New Layer (have Foreground set to Red when y'all do this). Lower the newly created layer.

Final¶

The prototype should now exist green on red, with no trace of blue!

This may not piece of work as well for you for 2 reasons:¶

• Photo's don't tend to take one colour you can choose similar that
• The foreground may contain portions of that colour that are removed by the plug-in

The work arounds, respectively, are:

• Apply multiple times, or merely once and affect-upwards by hand
• Paint underneath the new image with the original colour to bring it dorsum to those portions that need it

The original tutorial can be found here.

Source: https://www.gimp.org/tutorials/Changing_Background_Color_1/

Posted by: hoglundthatounhould.blogspot.com

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