Re: Properly dealing with images
Re: Properly dealing with images
- Subject: Re: Properly dealing with images
- From: Marcel Weiher <email@hidden>
- Date: Thu, 17 Jun 2004 12:57:30 +0100
On 17 Jun 2004, at 10:39, Michael Becker wrote:
I really don't know how to go about this one: My application basically
works with and on images. So far, everything works. I simply use
NSImages to display and manipulate the image data. However, here's my
problem:
Hmmm..if your app primarily deals with images, you probably don't want
to use NSImage.
NSImage doesn't seem to take into account that there are different
image resolutions. I have a 1800 x 1800 pixel image at 20 pixels per
inch. NSImage tells me that it's 6480 x 6480 pixels (which would be
true if it was at the standard 72 pixels per inch).
NSImage does not know about pixels. It is giving you the -size, which
is measured in (Postscript) points, which are 1/72 of an inch.
I need the *real* image dimensions
The -size method gives you the *real* dimensions, just not the number
of pixels. The Postscript/PDF imaging model that Quartz uses is device
independent, meaning measurements are in real units of length
(points/inches/centimeters/lightyears), not in device-specific measures
such as pixels.
(in this case that would be the 1800 x 1800) because I need to
calculate a quality factor for each image. And that one only depends
on the image size.
I am not familiar with TIFFRepresentations / BitmapRepresentations
(actually Representations in general), would they do me any good here?
If you are dealing with bitmap images, use NSBitmapImageRep. Forget
about NSImage. There, see -pixelsWide and -pixelsHigh.
Cheers,
Marcel
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