Thanks for all the feedback guys. I got it to work using the NSString
drawWithRect.
For the sake of all those who stumble across this thread, the code
used (minus lots of font and string code) is as follows...
unsigned char* bitmapData = 0;
NSBitmapImageRep* rep = [[[NSBitmapImageRep alloc]
initWithBitmapDataPlanes:&bitmapData // Single plane; just
our bitmapData
pixelsWide:width
pixelsHigh:height
bitsPerSample:8
samplesPerPixel:4
hasAlpha:YES
isPlanar:NO
colorSpaceName:NSCalibratedRGBColorSpace
bytesPerRow:0
// Let it compute bytesPerRow and bitsPerPixel
bitsPerPixel:0] autorelease];
[NSGraphicsContext saveGraphicsState];
NSGraphicsContext* context = [NSGraphicsContext
graphicsContextWithBitmapImageRep:rep];
[NSGraphicsContext setCurrentContext:context];
NSPoint origin = {0, 0};
NSSize size = {width, height};
NSRect rect = {origin, size};
[nsString drawWithRect:rect
options:NSStringDrawingUsesFontLeading|NSStringDrawingUsesLineFragmentOrigin
attributes:nsAttributes];
[NSGraphicsContext restoreGraphicsState];
returnData = [rep bitmapData];
And provided everything works as it should, returnData will contain
all the raw data of the bitmap.
Thanks
On Tue, Dec 1, 2009 at 5:54 AM, Adam R. Maxwell <amaxw...@mac.com> wrote:
>
> On Nov 29, 2009, at 10:01 PM, John Horigan wrote:
>
>>
>> On Nov 29, 2009, at 9:09 PM, Graham Cox wrote:
>>
>>>
>>> On 30/11/2009, at 2:44 PM, Glenn McCord wrote:
>>>
>>>> What I'm expecting is the drawAtPoint method to draw nsString inside
>>>> the bitmapRep of the NSContext at which point I can retrieve the raw
>>>> data and do something with it. On account of the data all being zero,
>>>> I'm obviously doing something wrong and would really appreciate some
>>>> advice.
>>>
>>>
>>> You also have to lock focus on the bitmap, which requires that it first be
>>> added to an NSImage (I think if you are targeting 10.6 only there is a new
>>> API that means you can avoid this).
>
> The OP was creating an NSGraphicsContext and making it the current drawing
> context, so I don't see a need to muck around with NSImage. The docs do say
> that you should only use -[NSString drawAtPoint:attributes:] when an NSView
> has focus, though. I know I've used -[NSString
> drawWithRect:options:attributes:] to draw to a bitmap context, so I'd give
> that a try (and be wary of the origin and flippedness of the context).
>
>>> Also, it's not necessary to allocate the bitmap's buffer - if you don't
>>> pass one, it will allocate it for you.
>>>
>>> --Graham
>>>
>>
>> Indeed, the initWithBitmapDataPlanes method treats the supplied buffer as
>> immutable and creates its own internal copy.
>
> This is not correct. From the docs [1]:
>
> "If planes is not NULL and the array contains at least one data pointer, the
> returned object will only reference the image data; it will not copy it. The
> object treats the image data in the buffers as immutable and will not attempt
> to alter it. When the object itself is freed, it will not attempt to free the
> buffers."
>
> Because of this, it's generally easier to let NSBitmapImageRep create the
> buffer for you, at least if you're going to be keeping it around.
>
>> You must request the bitmap back from the NSBitmapImageRep using the
>> bitmapData method. Prior to 10.6 the data backing up the NSBitmapImageRep
>> was a bitmap plane but in 10.6 the cocoa team changed the backing data for
>> NSBitmapImageRep to a CGImage. Either way, you should treat the data
>> returned by bitmapData as read-only (in case you were thinking of modifying
>> it).
>
> My understanding is that this only applies if you create the bitmap rep with
> initWithCGImage: (which is an odd limitation to keep track of). You can
> still modify bitmap data from ordinary NSBitmapImageRep instances, but it
> will be slow since NSBitmapImageRep has to recache. Of course, this is just
> my interpretation of the release notes [2] so I'd be interested in
> information to the contrary.
>
> [1]
> http://developer.apple.com/mac/library/documentation/cocoa/Reference/ApplicationKit/Classes/NSBitmapImageRep_Class/Reference/Reference.html#//apple_ref/occ/instm/NSBitmapImageRep/initWithBitmapDataPlanes:pixelsWide:pixelsHigh:bitsPerSample:samplesPerPixel:hasAlpha:isPlanar:colorSpaceName:bitmapFormat:bytesPerRow:bitsPerPixel:
>
> [2] http://developer.apple.com/mac/library/releasenotes/cocoa/AppKit.html
>
>
>
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