Re: CGImageRef printing issue
Re: CGImageRef printing issue
- Subject: Re: CGImageRef printing issue
- From: David Duncan <email@hidden>
- Date: Thu, 12 Nov 2009 14:46:23 -0800
On Nov 12, 2009, at 2:26 PM, Mirko Viviani wrote:
> On 12/ago/2009, at 21.30, David Duncan wrote:
>
>>> From my experience on Windows, DPIHeight and DPIWidth are properties of the
>>> display device the image is drawn on, and not properties of the image
>>> itself.
>>
>> They are properties of both. In the case of printing, you are using a fixed grid at 72 PPI. Your source image of course has its own DPI that determines the actual size of the image in real world units. You combine the two to print or display an image at its natural size.
>
> Do you mean that there is no way to print an image using a grid of 300 PPI with Cocoa/Quartz?
> If not, why? Alternatives?
Just like with all CGContexts you can apply a transform matrix to change the coordinate system. However in general this isn't necessary. If you want an image to display in a 1" x 1" area on screen, draw it into a 72x72 box. The pixel size of the image will determine DPI. If you wanted to draw a 1" image at 300 DPI then you would just need a 300x300 image drawn into a 72x72 box. If you wanted to draw a 1" image at 600 DPI then you would need a 600x600 image drawn into the same 72x72 box.
--
David Duncan
Apple DTS Animation and Printing
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