Re: 16 bit integer per colour bitmap graphics context

Subject: Re: 16 bit integer per colour bitmap graphics context

From: Martin Greenwood <email@hidden>

Date: Fri, 13 May 2005 17:42:24 +0100

Delivered-to: email@hidden

Thanks for the answers.

To be 100% certain, is there no way to use QDBeginCGContext on a graphics port with 16 bits per colour?

From your email I'm assuming there isn't, then I guess it could make sense to work entirely with 32 bit float per colour Quartz images.

Then at the end is there an easy way of accessing this image and extracting or converting to a 16bit integer per colour for copying into a graphics port?

By the way, I need the graphics port, because then the Quicktime image compression manager moves this into a Video Output.

Martin

On 13 May 2005, at 00:14, Derek Clegg wrote:

On May 12, 2005, at 2:07 PM, Martin Greenwood wrote:

This article suggests that 16bit per colour (b48r or b64a) images are supported by Quartz 2D.

http://developer.apple.com/qa/qa2001/qa1114.html

Yes, images with 16 bits/component are supported.

Whereas Table 2.1 here suggests that 8bit is the largest size for a colour.

Also true: a bitmap context is not the same thing as an image.

http://developer.apple.com/documentation/GraphicsImaging/Conceptual/drawingwithquartz2d/dq_context/chapter_3_section_4.html

When I try to create a bitmap graphics context the following happens..

CGBitmapContextCreate: unsupported parameter combination: 16 integer bits/component; 48 bits/pixel; 3-component colorspace; kCGImageAlphaNone.
or
CGBitmapContextCreate: unsupported parameter combination: 16 integer bits/component; 64 bits/pixel; 3-component colorspace; kCGImageAlphaPremultipliedLast.

Can I use Quartz to draw into b48r or b64a bitmaps?

No, you cannot. There's no support for > 8 bits/component (integer) bitmap contexts.

Derek

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References:
	>16 bit integer per colour bitmap graphics context (From: Martin Greenwood <email@hidden>)
	>Re: 16 bit integer per colour bitmap graphics context (From: Derek Clegg <email@hidden>)