Iterators over line and polygon on the pixels of the image data

[bmatthieu3]

From the image data iterator that read all the pixels of an image data unit, it could be great to get special methods

data.read_line<P: PixelType>(x1: u64, y1: u64, x2: u64, y2: u64) -> impl Iterator<Item=P>

that would impl something like brensenham to only seek over the pixels in the line between (x1,y1) to (x2,y2)

data.read_inside_polygon<P: PixelType>(p: &[(u64, u64)]) -> impl Iterator<Item=P>

that would only seek and return all the pixels inside a polygon (see https://medium.com/@dillihangrae/scanline-filling-algorithm-852ad47fb0dd)

These methods would be useful in astronomy for:

• getting all the pixel values of an image along a line
• computing the flux inside a polygon