Count 'em 1 M colours

Per the claim, this image has 1M different colours in it...

http://upload.wikimedia.org/wikipedi...6/1Mcolors.png
http://en.wikipedia.org/wiki/File:1Mcolors.png

--
-- r.p.e.35mm user resource: http://www.aliasimages.com/rpe35mmur.htm
-- r.p.d.slr-systems: http://www.aliasimages.com/rpdslrsysur.htm
-- [SI] gallery & rulz: http://www.pbase.com/shootin
-- e-meil: Remove FreeLunch.
-- usenet posts from gmail.com and googlemail.com are filtered out.

Alan Browne wrote:

Per the claim, this image has 1M different colours in it...

http://upload.wikimedia.org/wikipedi...6/1Mcolors.png
http://en.wikipedia.org/wiki/File:1Mcolors.png

Yes - it does have exactly 1 million different colours.
Some possibly interesting observations:

The png file is only 9,641 bytes.
Saved as an 8 bit tiff (with no embedded thumbnail), the file is
4,000,450 bytes.
Saved as jpeg using photoshop at quality 12 (maximum) file size is
480,886 bytes. Some image data is lost, as image data is reduced to
958978 different colours, but it still looks okay to me.
At quality 8 (high) file size is 207,569 bytes with 875,702 different
colours. Banding is quite clearly visible in the gradients which are
not visible in the original png.
Applying an ICC colour profile to the image (adobe wide gamut RGB) then
converting to working RGB, then resaving, colours are reduced to
417,087, and banding is more pronounced than with the high quality (8)
jpg - it looks very bad IMO.
PNG is a great format for this kind of image.

Me wrote:
Alan Browne wrote:

Per the claim, this image has 1M different colours in it...

http://upload.wikimedia.org/wikipedi...6/1Mcolors.png
http://en.wikipedia.org/wiki/File:1Mcolors.png

Yes - it does have exactly 1 million different colours.
Some possibly interesting observations:

The png file is only 9,641 bytes.
Saved as an 8 bit tiff (with no embedded thumbnail), the file is
4,000,450 bytes.
Saved as jpeg using photoshop at quality 12 (maximum) file size is
480,886 bytes. Some image data is lost, as image data is reduced to
958978 different colours, but it still looks okay to me.
At quality 8 (high) file size is 207,569 bytes with 875,702 different
colours. Banding is quite clearly visible in the gradients which are
not visible in the original png.
Applying an ICC colour profile to the image (adobe wide gamut RGB) then
converting to working RGB, then resaving, colours are reduced to
417,087, and banding is more pronounced than with the high quality (8)
jpg - it looks very bad IMO.
PNG is a great format for this kind of image.

What is it about PNG that allows 1M colors (24 bit/colour I assume (or
at least 20 bit, 2^201X10^6, slightly)) to be in a file less than 10 KB
in size?

--
-- r.p.e.35mm user resource: http://www.aliasimages.com/rpe35mmur.htm
-- r.p.d.slr-systems: http://www.aliasimages.com/rpdslrsysur.htm
-- [SI] gallery & rulz: http://www.pbase.com/shootin
-- e-meil: Remove FreeLunch.
-- usenet posts from gmail.com and googlemail.com are filtered out.

Alan Browne wrote:
[]
What is it about PNG that allows 1M colors (24 bit/colour I assume (or
at least 20 bit, 2^201X10^6, slightly)) to be in a file less than 10
KB in size?

1 - that PNG can encode the differences between current line and current
pixel and previous line and pixel.

2 - lossless compression (of a highly repeating difference pattern).

Cheers,
David