Trouble with Image offset in Accumulator (trimming)

pyramus's picture

Hi there,

I'm having some trouble with combining the Image Crop and Accumulator patches. I think I misunderstand how you can offset the image using the "Replacing Rectangle" values of the Accumulator:

  • Let's say I only need to display the horizontal middle portion of the image, so I want to trim the upper and bottom (please see my screenshot if this sounds complex -- it isn't supposed to be ;-)

  • Cropping the image works fine.

  • BUT when I feed this image into an Accumulator, things go weird: instead of the full trimmed area, the Accumulator seems to hold only the bottom portion of the image with a black area at the bottom. As if it just crops the image again until it fits into the defined size: "Pixels High" / "Replacing Rectangle (Height)", but then from the original top.

In other words, the Accumulator seems to just ignore the specified offset in Y direction, which -- which explains the black area. (again -- please check the screenshot, I think it's way more clear than me trying to write it down)

  • Note: I did try changing the numbers with "Replacing Rectangle" (especially Origin Y) from 0 to almost everything and even negative values, but that doesn't seem to make ANY difference. So clearly, I'm missing something.

Could anyone explain me how I should do this?

thx a lot!


CONTEXT (not really necessary for understanding my issue, but someone might wanna know): what I'm basically trying to do is trim the Input image BEFORE I feed it into any Core Image Filter, to prevent processing more data than I actually need. However, all cropping I do before any Accumulator in my composition (A LOT) is messed up after them. Hence, my whole output becomes F#*@! up.

After hours of trying without luck, I just gave in and made a quick hack around it by cropping all images AFTER processing them – which of course is pretty dumb and highly inefficient, but it works well enough – for now.... kindof. However, I'd still like to understand why this doesn't function like I think it should (probably: what I'm doing wrong).

Screen Shot 2013-01-23 at 1.43.32 .png
Screen Shot 2013-01-23 at 1.43.32 .png151.27 KB