which format of png should I use ?

Question

which format of png me should use Png-8 or png-24. which one is better for website. i am confused about these. what is main different between png-8 and png-24?

Answer 1

Png-24. Png-24 has alpha transparency (where Png-8 only has on/off transparency).

Png-8 is indexed. Png-24 is loss-less.

Png-24 is better in almost every way.

http://www.elated.com/articles/understanding-image-formats/

Answer 2

I would say that it depends on the image you want to store as PNG*, but in case you've doubts, PNG-24 is better: "true color" (8bits per channel), so that the image must not be dithered and don't "loose" "exact" color match, and optionally PNG-32 if with the alpha channel (transparency) too. PNG-8 images are limited (256 colors chosen from a 24bit palette) and allow only for a mask, you can use it e.g. if you convert from a GIF image; if you convert from other "true color" formats, you "loose" "exact" color match as said (the program try to reduce the real number of used colors into only 256 colors, and other tricks to give resemblance with the original). Some style of icons do not need "true colors", they are "described" well by 256 "fixed" colors or less, and so PNG-8 is ok; as said, if you have GIF images as source, go for PNG-8... if you convert from JPG, go for PNG-24; if you create you image by yourself directly "in" PNG, you know if you can "crunch" the result in PNG-8 or not, but if you are not able to evaluate or use tools to evaluate, PNG-24/32 is ok in any case.

Answer 3

PNG has several modes which can be used. It may contain:

• Greyscale
• Indexed colour, usually meant by PNG-8
• Greayscale with alpha
• Truecolour (RGB)
• Truecolour with alpha (RGBA), usually meant by PNG-24

Indexed colour is different from the others that it is a palette of maximum 256 colours, from which indexes are used to denote the colour of specific pixels. It can contain transparency via an auxillary chunk. So every pixel is denoted by a byte-wide value or even less if palette isn't that big. If you use truecolour, there will be more data per pixel, depending on whether you use an alpha-channel.

So in a large image indexed colour will save you a lot of data per each pixel. However, if you use more than 256 colours, some colour data will be lost, which is also more probable in a large image. I would advise to save your image in both formats and see if the loss is worth the gain in smaller file size. Though if you are designing your image for normal web site, not for mobile phones, you should better use PNG-24 anyway, since no one will notice the difference in the size.