Change all white pixels to transparent in a saved image file


What's the easiest/best way to change all white pixels to transparent in a saved image file?

For example, I've got a .png file of a (black on white) signature which was created using the Snipping Tool in Windows 7. However, whenever I apply it to a document (eg Word, PowerPoint, etc) by clicking Insert > Picture > Filename, it comes as a block with the white portions obscuring whatever is behind it.

I'd like to modify it somehow so that only the non-white pixels are inserted and all of the white area is transparent.

I've got MS Paint of course and also Inkscape but not Photoshop, etc. I've looked up a couple of webpages re creating transparent images in Inkscape and although I've followed the instructions they've included, I must be doing something wrong because the resulting files are not transparent.

I can upload the .png file or one that's similar if that would be helpful.

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Dave BaldwinFixer of ProblemsCommented:
GIMP can do that for you and it's free.
WeThotUWasAToadAuthor Commented:
Additional note:

In reading about this, I've found places that refer to making the "background" of an image transparent and others that mention changing one particular color to another. At first I assumed the white area in my snipped screenshots to be the background but now I'm wondering if it is not actually the background but an area of  particular color, in this case white.

Is that a relevant point?
Joe Winograd, Fellow&MVEDeveloperCommented:
Hi Steve,
One of my EE articles shows exactly how to do that:
Signature Image with Transparent Background

The article is about an image with a signature, but, of course, the technique will work to change the white pixels of any image to be transparent. And if one of your uses for it is with PDF files, this EE article shows how to make a stamp out of it in Acrobat:
Create Signature Stamp in Adobe Acrobat

Regards, Joe

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Nichole LaRueMarketing OperationsCommented:
GIMP is free and easy to use. Open file in GIMP > Under Layer tab navigate down to transparency < Chose color to alpha. That will remove the white and you can save as a png.
as it is a png a quick fix is to save it as a jpeg load it into MS Paint and go t save as.. then it should load into your word etc
You can change the output to jpeg with the snipping tool choose save as,
To give you more choices as we differ on the simplicity of Gimp for a has considerable learning curve
Forget Inkscape for this it is a great tool
MS Paint is not good enough as it doesn't have the tools
The best and simplest tool free for you is Paint net
There is tons of plugins for it

Yes please post/attach your image and I'll show you how to do it using Paint net.
For example
Load your text image on as new image , drag and drop
click the magic wand and touch the image  you'll see the dotted lines all over it go to file top left  EDIT and click on invert
invert selection magic wand PDN then edit copy edit paste as new image it is now black transparent text go to file save as. png
transparent textThere is an arrow at the top to undo
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