HowCanIConvertAnNSArrayOfValuesToAnNSImage

Sorry, I’ve tried the docs, searching the CocoaDev website and the Cocoa-dev list archives, but haven’t found much pertaining to my problem. This must be a really strange request.

I have an NSArray of values that I want to convert to an NSImage, preferable TIFF format?, for drawing in an NSView. How can I do this? I believe the key is setting up an NSCustomImageRep. But what then?

Example

array value NSColor

1 [NSColor redColor]

2 [NSColor greenColor]

. . . .

I’m able to understand most Cocoa classes enough to begin to use them and then gain understanding, but NSImage beyond simple import and display is eluding me.

Thanks for any help.

Hmm. I’m not quite sure what you mean. There’s no natural meaning of “convert a value to an image”. I suppose for a color, you might want to create an image with some particular dimensions filled solid with that color? Is that what you’re after?

I think your description is correct. I’ll try to elaborate further.

I have a 2x2 matrix of elevation values stored in an 1-dimensional NSArray where each value represents the elevation within that square area, say 10 x 10 feet. Now I want to make a gray-scale image where higher elevations are light and lower elevations are dark. So I want to make an image where each value is represented by a single pixel (which represents the 10x10 feet area) and I want to make all pixels with a particular elevation value the same shade of gray.

I want to also extend this so that instead of gray-scale, I can assign a particular color to each pixel representing a certain value.

I hope this makes more sense.

Try something like this (I recommend that you supplement this with a quick visit to Apple’s online docs):

Create an empty NSImage using initWithSize:.
Create an NSBitmapImageRep with the required dimensions, colorspace and so on (the initializer for doing this has one of the longest signatures in Cocoa: initWithBitmapDataPlanes:pixelsWide:pixelsHigh:bitsPerSample:samplesPerPixel:hasAlpha:isPlanar:colorSpaceName:bytesPerRow:bitsPerPixel:.
Add the NSBitmapImageRep to the NSImage.
Get yourself ready to draw your data.
Call the lockFocusOnRepresentation: method of your NSImage. This method basically tells Cocoa and CoreGraphics to treat the NSImageRep as the current drawing canvas.
Draw your data using the AppKit drawing functions (eg. NSRectFill) or CoreGraphics.
Call the unlockFocus method of your NSImage, to restore the previous drawing canvas.
Your NSImage has a method called TIFFRepresentation, which will give you an NSData object containing TIFF data.

-ToM

I found an example of something similar to what I wanted to do here: http://www.macdevcenter.com/pub/a/mac/2002/08/06/cocoa.html . It does exactly what ToM outlined, but includes sample code which I needed to understand the process.

Thanks ToM. You got me along the correct path.