Re: NSReadPixel returning different colors
Re: NSReadPixel returning different colors
- Subject: Re: NSReadPixel returning different colors
- From: Shamyl Zakariya <email@hidden>
- Date: Mon, 8 Jan 2007 11:26:15 -0500
You may have to go directly through libpng; that will give you direct
access. I -- grudgingly -- did it since I needed to get image data
from PNGs without Cocoa pre-multiplying the alpha channel. If going
through libPNG is too much of a PITA, and if your color map is small,
you might just use a simpler uncompressed format like tiff, or raw,
and write your own accessor.
email@hidden
In the same episode, the scientist suggests that the
debigulation can only be reversed by a rebigulator.
-- wikipedia
On Jan 8, 2007, at 10:44 AM, John Stiles wrote:
Does the PNG have any gamma information in it? I am pretty sure
that the OS changed at some point to honor the gamma; previously I
believe it was ignored. So you might want to remove any gamma info.
Richard Holliday wrote:
On Monday, January 08, 2007, at 10:07AM, "Andreas Mayer"
<email@hidden> wrote:
Am 08.01.2007 um 15:32 Uhr schrieb Richard Holliday:
The original pixel color in the PNG file is R:153 G:255 B:153.
On the 10.4 machine I get back R: 0.6 G: 1.0 B: 0.6
On the 10.2 machine I get back R: 0.53 G: 1.0 B 0.53
I understand this is being color adjusted by the system but I
just need the raw values with nothing adjusted in any way.
You mean on 10.2? Well, that might just be a bug.
The values reported from 10.4 are without any adjustment. 0.6*255
= 153
Correct, the 10.4 values are fine it's just from 10.2.8.
Also, I tried my own code which returns the RGB values via the
[NSBitmapImageRep bitmapData] member. This has exactly the same
problem which lead me to believe I'm missing something else. As
soon as the PNG becomes an NSImage the data gets translated some how?
There must be a way to get the original data before OSX / Cocoa
"messes" with it.
Richard
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