Page 1 of 1

Crop image into polygon shape

Posted: Fri Oct 09, 2009 8:28 am
by deadfish
Hi Everyone (this is my first post),

I am trying to figure a way of cropping a polygon out of an image. I have been reading other similar code. It seems that most code is based around the following process:

-Resize the image to fit the width and height of the polygon shape,

Create a blank image of an unusual colour the same size,

Overlay transparent pixels in the shape of the polygon,

Overlay that on to the resized image

set the unusual colour to be transparent...

like http://www.google.co.uk/url?sa=t&source ... WWl8jo3J7g


My problem is I do not want the code to be reliant on the unusual colour not being in the original image. Does anyone have a better method or some code which I can use to check if the unusual colour is in the image.

Thanks in Advance.

Re: Crop image into polygon shape

Posted: Fri Oct 09, 2009 11:44 am
by desperado
why not just use a .png mask as png supports transparency/alpha?

Re: Crop image into polygon shape

Posted: Fri Oct 09, 2009 12:49 pm
by deadfish
..But what I want is the final image inside the shape to be surrounded by transparency.

So once I have masked it the mask will have a colour which I must then make transparent... but if that colour is in the image then that will be ruined too. So either I am looking for a better way of masking or a way of looking through the image to find a colour not present to use as the mask colour.

Thanks :)