PNG: Quality, depth, colors, bits

Questions and postings pertaining to the usage of ImageMagick regardless of the interface. This includes the command-line utilities, as well as the C and C++ APIs. Usage questions are like "How do I use ImageMagick to create drop shadows?".
Locked
colorful
Posts: 6
Joined: 2020-03-04T11:55:05-07:00
Authentication code: 1152

PNG: Quality, depth, colors, bits

Post by colorful »

Quality, depth, colors, and bits.

What are the differences?

I am trying to reduce the size of PNG.

snibgo
Posts: 13034
Joined: 2010-01-23T23:01:33-07:00
Authentication code: 1151
Location: England, UK

Re: PNG: Quality, depth, colors, bits

Post by snibgo »

"-quality" for PNG refers to parameters of the lossless compression method.

"-depth" is the number of bits/channel/pixel. For PNG, this is 8 or 16.

A "bit" is a binary digit.

A "color" is, well, a colour.

To reduce the size of PNG files, I suggest the program "pngcrush".
snibgo's IM pages: im.snibgo.com

colorful
Posts: 6
Joined: 2020-03-04T11:55:05-07:00
Authentication code: 1152

Re: PNG: Quality, depth, colors, bits

Post by colorful »

What is the default quality of PNG in 'convert'? When I use 'identify' it does not show quality. Shows for JPG, but not PNG.

I am only seeing 8 depth in the PNGs. When is 16 depth used?

Does 'color' use 255 or 256 format? How do I see other color number options?

pngcrush looks like is used for existing PNG. I am looking to convert JPG to PNG, but the size difference is significant.

User avatar
fmw42
Posts: 26383
Joined: 2007-07-02T17:14:51-07:00
Authentication code: 1152
Location: Sunnyvale, California, USA

Re: PNG: Quality, depth, colors, bits

Post by fmw42 »


Locked