Re: NSReadPixel returning different colors
Re: NSReadPixel returning different colors
- Subject: Re: NSReadPixel returning different colors
- From: Richard Holliday <email@hidden>
- Date: Mon, 08 Jan 2007 08:47:08 -0800
On Monday, January 08, 2007, at 10:42AM, "John Stiles" <email@hidden> 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.
Thanks for that tip John.
I removed the gamma information (using GammaSlammer) but had the same results. After further reading though it looks as if 10.4 adjusts the gamma for a PNG even if there is no gamma in the file itself.
As a test I converted the file to a BMP format and the pixel color routine works perfectly on both platforms.
If this is in fact a problem inherent to PNGs then I'll have to switch file format when I need exact pixel matching.
Thanks,
Richard
>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
>> _______________________________________________
>>
>
_______________________________________________
Cocoa-dev mailing list (email@hidden)
Do not post admin requests or moderator comments to the list.
Contact the moderators at cocoa-dev-admins(at)lists.apple.com
Help/Unsubscribe/Update your Subscription:
This email sent to email@hidden