Before posting any PNG images on here, I use the open source Pngcrush tool to compress the images as much as possible first. Even when I set the compression to its highest value in programs like IrfanView, Pngcrush is still able to make most images even smaller.
Unfortunately Pngcrush is a command-line tool, so it’s not the easiest tool to use in Windows. So here’s how to add a ‘Crush’ option to the context (right-click) menu in Windows Explorer for quicker crushing.
Firstly, you’ll need to download Pngcrush, which is availble at Sourceforge. You’ll want the win32 version. Download it and unpack it somewhere.
The instructions that follow are for Windows XP; for older versions they’ll be a little different.
Open Control Panel and choose Folder Options. Select the File Types tab, and scroll down to the ‘PNG’ entry. Click on ‘Advanced’, then click on ‘New…’.
In ‘Action’, type Crush, and in ‘Application used to perform action’, type the following:
C:\Downloads\pngcrush\pngcrush.exe -e 2.png "%1"
The first portion should be the location of the pngcrush.exe file that you extracted from the archive. The ‘-e 2.png’ bit specifies what the outputted PNG image will be called, which in the case it’ll be the filename with ‘2’ appended to it (so the crushed version of ‘catpicture.png’ would be called ‘catpicture2.png’). You could also use the following:
C:\Downloads\pngcrush\pngcrush.exe -brute -e 2.png "%1"
This does the same as the above but does a ‘brute force’ crush – rather than use one of a few common methods to crush the file, it will use all of them. It’ll take longer, especially on older hardware, but may result in a smaller PNG file.
And you’re done. Now, when you right-click on a PNG file, you can select ‘Crush’ and have Pngcrush your image for you. Remember that the compression is lossless – you won’t lose any quality by using the tool.