PNG image compression -PunyPNG ,Smush.it and more

PunyPNG is a free website optimization tool that dramaticallyreduces the file size of your images without any loss of quality.
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1. You need to register !

Smush.it is a "lossless" tool, which means it optimizes the images without changing their look or visual quality. It provides a downloadable zip file with the minimized image file after compression.
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Here is another compression tool in which you compress your image by your own work ! Follow as shown below.

Step 1. Download PngCrush
Step 2. Unzip contents to desktop with Folder name PNGCRUSH using Winzip or othertools 

Step 3. Go to command prompt ( window key + r , then type cmd )  

Step 4. In opened window type cd desktop. After that , type cd pngcrush and press enter.

Step 5. now type pngcrush -brute input.png yourname.png
Where input is the name of your input file in that folder

Important : You must keep the image file in same folder as that of pngcrush !

Step 6. Got yopur file compressed ? Just leave a comment ! 

PNGOUT is a tool which can optimize PNG files created by other programs. It can be run from the Windows Run dialog box or at the command prompt.
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Tutorial is here..

 PNG Monster is a PNG compression GUI designed to very easily compress large numbers of PNG files automatically with the lowest possible file sizes without any visual change.It can be downloaded Here.

Unzip the file to some folder and place your png file in that folder.
Just press run and , it rally compresses your image a lot ! Try it ?

Just select the files you want to optimize (or drag them onto the 
window), select where you want them to go, and click the button. PNGauntlet can also be used to convert JPG, GIF, TGA, PCX, and BMP files to PNG.Download Here