Make the background of an image transparent Solved

Question

Hello!

Some images have a transparent background, I mean there is no white square around the drawing, for example. How can I make the background transparent, using software or something else?

Thank you.

Configuration: Windows 7 / Internet Explorer 9.0

Le Gnou · Accepted Answer

Hello,

The first thing to know when talking about transparency is that not all image formats handle it the same way.

As an example, here are 3 common formats:

The JPG/JPEG format does NOT support transparency,
The GIF format only handles two levels of transparency (in addition to being limited to 256 colors),
The PNG format supports 256 levels of transparency.

So, if you are using a JPG image, for example, you will need to save it as a PNG after making parts of the image transparent, otherwise that transparency will not be preserved.
;)

The second thing is that you need to add an alpha channel: it's what will contain the transparency information (which parts will be transparent, with what level of transparency...).
;)

On the software side:

Photofiltre 7 (free): http://www.commentcamarche.net/download/telecharger-34090233-photofiltre-7
- /!\ Warning, as specified:
- The installation version includes the Ask Toolbar. Uncheck the option during installation if you do not want to install it.
Gimp (free and open-source): https://www.commentcamarche.net/telecharger/photo-graphisme/11145-the-gimp/

An example, with this image:
https://pix.toile-libre.org/upload/original/1360212716.jpg

Since the image is in JPG format, the first thing: add an alpha channel.

In Photofiltre 7: Image > Mode > RVBA (alpha channel)
In Gimp: Layer > Transparency > Add Alpha Channel.

Then... well, select the parts of the image you want to make transparent, and delete...

The selection tools in Photofiltre 7:
https://www.cjoint.com/13fe/CBhgh5BBIh0_capture01.jpg
If you want to remove a whole color, like here, the black, Image > Transparency Color. In the window that appears, choose black:
https://pix.toile-libre.org/upload/original/1360213907.jpg

Once the areas are transparent: File > Save As, and choose PNG.
;)

With Gimp, the principle is the same, add an alpha channel, use the selection tools:
https://pix.toile-libre.org/upload/original/1360214250.jpg
...and delete the parts of the image...

You can also choose to remove a color globally like in Photofiltre: Layer > Transparency > Color to Alpha.
Then, File > Export, and there too choose PNG.
;)

Note that in both software, to indicate which parts are transparent, they appear as a checkerboard pattern:
https://pix.toile-libre.org/upload/original/1360214795.jpg
... this checkerboard is only there to show you the transparent areas and will not be visible once the image is saved...
;)

More info on transparency and the alpha channel:
http://leblogdugnou.blogspot.fr/2012/03/transparence-et-canal-alpha-images.html
http://leblogdugnou.blogspot.fr/2012/12/retour-sur-le-canal-alpha.html
;)

@+

(_._)
-0|0-

transalpin · Answer

Hello,

After some varied responses, we are getting to the heart of the matter regarding the masking issue.

Two techniques can be used:

1) We create a selection using various tools. The best tool is the "Pen" tool.
This tool is not available in PhotoFiltre but is available in Gimp.
Then we remove the part that is not selected.
This method is simple but poses a problem when we want to, for example, mask hair.

2) We use the fill tool which will remove all colors close to a reference color.
This tool can yield excellent results when the background is contrasting and uniform.
However, this tool, which works on an all-or-nothing basis, may disappoint some.
Photoshop has developed an interesting tool that refines the masking by incorporating two components: gradient and decontamination.
Labography, a free software, also offers this possibility. Indeed, when we mask hair, we are working on very fine areas and when we zoom in on the obtained result, it becomes awful due to a jagged effect. By adding a slight gradient, we can easily overcome this.

The issue you raise regarding the lack of contrast is very interesting.
Generally, it can be solved by selecting everything except the subject to be masked. This is done roughly, of course.
For this, we use either a "selection brush," the "Pen" tool, or the "quick selection" tool, etc.
Another method consists of selecting the subject to be masked, then inverting the selection.

In fact, there is no miracle cure. Each photo is a particular case and we must find the right tool for each case.

@+

Make the background of an image transparent

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