Resize .PNG (filesize) but keep dimensions

[RabbieBurns]

IVe got an image and it needs to be under a certain filesize, but it needs to be a certain width and height. It also has to only be a png.

 

I cant figure out how I can reduce the size of it without reducing its dimensions?

 

I have CS3 and MSPaint available.

 

How do i Do it ?

[localzuk]

PNGs store data as either 8bit, 24bit or 32bit colour, with or without alpha transparency. So, the way you'd reduce the size of the image is to lower the quality level, and alter the dithering to your satisfaction. This is usually done on save-as in most programs. I'm not familiar with CS3, and Paint is no use. Personally, I use Paint.Net.

 

There used to be a web optimizer tool in Photoshop, you may be able to use this. It was called 'Save for Web' or similar, and allowed you to play around with the file quality settings and see in realtime the changes made.

[powdarrmonkey]

Maximise the number of sharp transitions between colour edges and minimise the number of colour details used (solidify the background colour, for example). Disable Adam-7 interlacing if it is being used.

 

The compression technique is discussed in detail on Wikipedia: Portable Network Graphics - Wikipedia, the free encyclopedia

[echo]

You need to save as a PNG8 which use 256 colours, I expect the program you are using will default to PNG24 or PNG32. I've only got Fireworks CS4 to try it on but I can select the type of PNG under the optimise menu.

 

Hope that helps.

[ICT_GUY]

PNG is a lossless format, unlike JPEG you cannot increase the "compression". Reducing the bit depth and simplifying the image two options. In photoshop you can resize the image (reduce the pixels) and reduce the DPI but keep the same image dimensions. It will just not be as sharp. You can do this with the crop tool by specifying the physical size and the dpi. The downside is loss of detail as a 12" x 8" photo at 300dpi has 4 times the amount of pixels as a 12" x 8" one at 150dpi.

 

Hope this helps.

[RabbieBurns]

Thanks, think Ive got it looking alright now