Java rotation of pixel array

Question

I have tried to make an algorithm in java to rotate a 2-d pixel array(Not restricted to 90 degrees), the only problem i have with this is: the end result leaves me with dots

Answer 1

You are pushing the pixels forward, and not every pixel is hit by the discretized rotation map. You can get rid of the gaps by calculating the source of each pixel instead.

Instead of

for each pixel p in the source
    pixel q = rotate(p, theta)
    q.setColor(p.getColor())

try

for each pixel q in the image
    pixel p = rotate(q, -theta)
    q.setColor(p.getColor())

This will still have visual artifacts. You can improve on this by interpolating instead of rounding the coordinates of the source pixel p to integer values.

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Edit: Your rotation formulas looked odd, but they appear ok after using trig identities like cos(r+pi/2) = -sin(r) and sin(r+pi/2)=cos(r). They should not be the cause of any stretching.