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Revealing sections (expanding circles) of a jpeg

February 26, 2014 | 6:06 am

Hi all,

i am trying to reveal a certain section of a jpeg (an expanding circle).

A jpeg will remain black until a point in time that i want to reveal a shape within the window, thus slowly revealing the section of the jpeg behind, while keeping the rest of the jpeg hidden.

Does anybody know how i could do this?

I have got as far as to getting a jpeg into a matrix, and then unpacking it, and then altering the alpha channels so that i start from a black image and then move to reveal the picture, but how would i go about revealing certain sections of the picture?

Any help would be much appreciated. File attached as far as i have got so far…

https://copy.com/EkQ2Zk2MOJpob9Kr

thankyou in advance!


February 26, 2014 | 8:51 am

Suggested reading:

Jitter Tutorial 29: Using the Alpha Channel

Example:

<code>

– Pasted Max Patch, click to expand. –

</code>


February 26, 2014 | 4:08 pm

that has helped so much, thankyou Christopher, and god bless these forums ;-)


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