Re: Getting Pixel Position in an image

FROM : Guy English
DATE : Tue Dec 21 22:56:07 2004

Hi,

    Once you work out where you are in the image view space you'll
need to transform your point one final step - into the scalled image
space. For this you'll need to know a) how scaled your image and b)
the lower left hand point (or top-left if the view is flipped) of the
visible region of the image (in image space - ie the pixel point).
Then you just do
image_space_click.x = (mouse.x / scale) + image_visible_frame.origin.x
image_space_click.y = (mouse.y / scale) + image_visible_frame.origin.y

Hope fully that helps.

Guy


On 21 Dec 2004 07:26:15 -0000, Anish Kumar <<email_removed>> wrote:
>
>
>    Hi All,
> 
>  Can anyone please tell me how to get the "Pixel position" of a pixel that
> is currently under
>  the mouse for an image that is displayed in a sub-class of NSView. I know
> how to get the
>  current mouse location in the image views co-ordinates, but I can't use
> this value in my
>  application for the following reason.
> 
>  Basically I am developing an annotation feature for my application (Similar
> to ACROBAT's
>  annotation feature) and the user can enter their comments/annotation for
> the image and a
>  icon will be placed on the location where the annotation was made to the
> image. Clicking
>  the icon will display the annotation that was made there.
> 
>  The problem I face here is:- as long as the image is not zoomed, the
> annotation icons are in
>  their correct position. When I zoom the image, the icons are misplaced as I
> am using the
>  mouse locations for placing the icons to the image. Now if I use the PIXEL
> POSITION in the
>  image instead of the mouse location I can place the annotation icons at the
> correct pixel
>  position irrespective of the zoom-level of the image.
> 
>  So can anyone please tell me how to get the pixel-positions in an image.(
> something similar
>  to  Adobe photoshop's INFO window, where they display the X-Y coordinates
> of the cursor,
>  that doesn't change for a particular position in the image even if the
> image is zoomed
>  (zoom-in or zoom-out) to any level.
> 
>  thanks in advance,
>  -Anish
>
> 
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