imageoptim.com

ImageOptim is a free app that makes images take up less disk space and load faster, without sacrificing quality. It optimizes compression parameters, removes junk metadata and unnecessary color profiles.

ImageOptim seamlessly integrates the bes ...

smashinghub.com/optimize-your-images.htm

Optimizing your website images is a smart way to make your website’s page load more quickly and at the same time save bandwidth consumption and obviously, your hosting bills.

Many tools for optimizing your website images are present out t ...

www.imgopt.com

This is a web-based tool for using Yahoo's smush.it service making the whole process much easier.

NB: The Yahoo smush.it service has been discontinued but this site might re-task to an open source version of the service.

www.resmush.it

reSmush.it is a FREE alternative to Yahoo Smush.it (which discontinues on March 2015). This tool provides an online way to optimize pictures size via a documented webservice. reSmush.it is 100% compatible with old Yahoo Smush.it API.

There is c ...

photography.tutsplus.com/articles/creating-real-layer-masks-...

Photoshop is not the only program able to do layer masks, a  fast and clean way to mix elements from different images in one final picture. You can do it for free with software like GIMP. Or Perfect Layers 2. In this tutorial we show you how.

gimp-savvy.com/BOOK/index.html?node45.html

Grokking the GIMP is a leading book for learning advanced digital image editing techniques using the GNU Image Manipulation Program, the GIMP. The book provides everything needed to learn the GIMP, including tutorials, beginning and advanced techniques ...

docs.gimp.org/en/gimp-concepts-layer-modes.html

GIMP has twenty-one layer modes. Layer modes are also sometimes called “blending modes”. Selecting a layer mode changes the appearance of the layer or image, based on the layer or layers beneath it. If there is only one layer, the layer mod ...

www.gimp.org/tutorials/Layer_Masks/

Layer masks are a fundamental tool in image manipulations. They allow you to selectively modify the opacity (transparency) of the layer they belong to. This differs from the use of the layer Opacity slider as a mask has the ability to ...

www.youtube.com/watch?v=9ErchKGzsNc

GIMP photo editing; beginner tutorial learn what a mask is, how to add a layer mask, paint it, copy & paste a mask and more.

blog.irisquest.net/2008/06/gimp-copy-layer-mask-to-another-l...

Did you ever need to copy a layer mask from one layer to another? In Photoshop this is a very easy process, which involves only the mouse and the Ctrl key, but in GIMP things aren't that straightforward (but not much complicated either).

www.youtube.com/watch?v=y_2R-OQddyM

Like the title says - How to blend two images together using Layer Masks. Simple! Special thanks go to Vincent for these images.

paint.net.amihotornot.com.au/Features/Effects/Plugins/Object...

Paint.NET alpha mask plugin example.

paint.net.amihotornot.com.au

The best free graphic and media editing software with alot of plugins.Paint.NET. Thgis is not the official homepage but contains an excellent plugin repository which is all nicley arranged.

forums.getpaint.net/index.php?/topic/13000-otherfarmcolorrep...

This effect enables you to remove/change a color (with a tolerance)

* choose a color you want to remove/change
* set a tolerance for this color (0= use this exact color till 100 = all colors)
* select the replacing color (transparen ...

forums.getpaint.net/index.php?/topic/1854-alpha-mask-import-...

This plugin allows you to import an image from a file or the clipboard and make it an alpha mask. If the image has color, it will be converted to greyscale.

Version 2.0 adds the ability to use whatever image is on your clipb ...