Re: how to get a sub piece of an NSImage or make a new NSImage that is a subset of an existing one

FROM : Jonathan Grynspan
DATE : Sat Aug 12 07:43:25 2006

You can find more information on Cocoa's graphics model at http://
developer.apple.com/documentation/Cocoa/Conceptual/CocoaDrawingGuide/
index.html . Of particular interest to you may be the sections on 
Graphics Contexts and Images.

-Jonathan Grynspan

On 12-Aug-06, at 1:34 AM, Chad Leigh wrote:

>
> On Aug 11, 2006, at 11:28 PM, Jonathan Grynspan wrote:
>

>> Try the following:
>>
>> NSImage *partOfImage(NSImage *input, NSRect targetRect) {
>>     if (input) {
>>         NSImage *output = [[NSImage alloc] initWithSize: targetRect.size];
>>         [output lockFocus];
>>         [input
>>             drawAtPoint:    NSZeroPoint
>>             fromRect:    targetRect
>>             operation:    NSCompositeCopy
>>             fraction:        1.0f];
>>         [output unlockFocus];
>>         return [output autorelease];
>>     } else {
>>         return nil;
>>     }
>> }

>
> Thanks, I will.  I've been reading the lockFocus and the 
> drawAtPoint stuff since I posted the first request, trying to put 
> my brain around it.  This helps immensely!
>
> Thanks
> Chad
>

>>
>> -Jonathan Grynspan
>>
>> On 12-Aug-06, at 1:17 AM, Chad Leigh wrote:
>>

>>> I have a Cocoa app and I get a PDF image over the internet that I 
>>> store in an NSImage using
>>>
>>>    label = [[NSImage alloc] initWithData:finalImage];
>>>
>>>
>>> The image previously was a PNG image and was exactly the image 
>>> needed.  Now that they pass a PDF image, they pass an image that 
>>> is an image of a complete piece of paper with the image I am 
>>> interested in placed on the upper half of this virtual paper (the 
>>> rest is just blank).  The image is always in the same place and 
>>> the same size so I can determine a Rect that will always work to 
>>> select it.  I want to extract this image out of the PDF and 
>>> create a new NSImage (or overwrite the old one, I don't care) 
>>> that I can use later on to print in my own existing print routine 
>>> and to display thumbnails of it.
>>>
>>> I do not see how to go about it.  Most of the draw/composite 
>>> routines I see in NSImage rely on an existing userspace to draw 
>>> into.  I want to "draw" into a new NSImage.  My brain is having a 
>>> hard time adjusting to think about how to do this.
>>>
>>> Ideally I want something like
>>>
>>>     NSImage *newImage = [[NSImage alloc] initFromImage:oldImage 
>>> usingRect:targetRect];
>>>
>>> I expect what I want to do is very easy but if someone could 
>>> point me on the way I should be exploring I would appreciate it.
>>>
>>>
>>> Thanks
>>> Chad
>>>
>>> _______________________________________________
>>> MacOSX-dev mailing list
>>> <email_removed>
>>> http://www.omnigroup.com/mailman/listinfo/macosx-dev

>>
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>
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