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How do I create an NSBitmapImageRep from scratch?

First: I want to use NSBezierPath

to draw some simple buttons in my application, so I suppose I have to create NSBitmapImageRep

, get CGImage

, create NSImage

and then call setImage: on the button. Correct me if I am wrong.

So I went to see how to create NSBitmapImage

and found this: **initWithBitmapDataPlanes:pixelsWide:pixelsHigh:bitsPerSample:samplesPerPixel:hasAlpha:isPlanar:colorSpaceName:bitmapFormat:bytesPerRow:bitsPerPixel:**

Wow.

Remembering that what I was looking for was something like a string initWithSize:

, what should I use for these values?

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3 answers


Any specific reason why you don't just create a new one NSImage

and draw into it by copying the focus-locked drawing code like

NSImage* anImage = [[NSImage alloc] initWithSize:NSMakeSize(100.0,  100.0)];
[anImage lockFocus];

// Do your drawing here...

[anImage unlockFocus];


( Cocoa Drawing Guide is your friend by the way)

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The documentation explains it pretty well.

The parameter is a planes

little confusing. It's basically a pointer to a pointer to pixels. So if you have pixels in an array pointed to by a variable named "pixels", for example:

unsigned char* pixels = malloc (width * height * 4); // assumes ARGB 8-bit pixels
NSBitmapImageRep* myImageRep = [[NSBitmapImageRep alloc] initWithDataPlanes:&pixels
... etc...];


The rest of the parameters are pretty simple. pixelWidth

and pixelHeight

is what you expect. The rest of the values ​​correspond to how your data is ordered. Are you using 8 bits per channel ARGB data? Or is it RGBA at 32 bits per channel?

NSDeviceRGBColorSpace

probably sufficient for use in a color space.

A pipe isPlanar

must be NO

if you are passing a single pointer to your image data.

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You don't need to allocate space for the data planes. Below is the call to create an empty 32 bit NSBitmapImageRep

with alpha component.

NSBitmapImageRep *newRep = [[NSBitmapImageRep alloc] initWithBitmapDataPlanes:NULL
                                                                   pixelsWide:pixelsWide
                                                                   pixelsHigh:pixelsHigh
                                                                bitsPerSample:8
                                                              samplesPerPixel:4
                                                                     hasAlpha:YES
                                                                     isPlanar:NO
                                                               colorSpaceName:NSDeviceRGBColorSpace
                                                                   bytesPerRow:4 * pixelsWide
                                                                  bitsPerPixel:32];
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