Re: drawing an array of pixels to the screen
Re: drawing an array of pixels to the screen
- Subject: Re: drawing an array of pixels to the screen
- From: Jason Horn <email@hidden>
- Date: Mon, 12 Nov 2007 07:50:22 -0500
John,
Thanks for your thoughts here, but you've hit exactly on the problem.
NSBitmapImageRep takes a byte array, NOT a 2d array of pixel values.
That means after every analytical operation I perform on the 2d pixel
array, I have to then transform it back into a byte stream (or at
least a flat array) before drawing it. This slows everything down.
AFIK, NSBitmapImageRep will not take a 2d array of values. (I've
tried). The crux of my question was, once you have a 2d array (x,y)
arrangement of pixels, what's the fastest way to get it onto the screen.
- Jason
On Nov 9, 2007, at 11:56 PM, John Stiles wrote:
+NSBitmapImageRep
initWithBitmapDataPlanes:pixelsWide:pixelsHigh:bitsPerSample:samplesPerPixel:hasAlpha:isPlanar:colorSpaceName:bitmapFormat:bytesPerRow:bitsPerPixel
: is pretty efficient. You're not copying the whole byte array, it
just takes a reference to it.
However, another poster hit the nail on the head—if performance is
important to you, might as well go OpenGL. You can't get any faster
than that on OS X.
On Nov 9, 2007, at 7:27 PM, Jason Horn wrote:
I am working on a computer vision based app that detects objects in
video images. I have to implement custom algorithms to locate and
track objects, so I need to write code that has direct access to
the pixel values and keep track of the x,y coordinates of certain
objects. This is easiest to do with the image represented as a 2D
array of int values. However, it seems that the only way to draw
bitmaps to the screen is with NSImage and NSBitmapImageRep or
CIImage. Is there another way? It seems like a waste (and a
performance hit) to convert a 2D array of pixel values into a byte
stream every time you want to display the image. Is there a way to
draw the pixel values directly to the screen (and do it quickly).
Thanks for any ideas.
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