Image rotation * without resizing

Question

I would like to rotate the image (with a given rotation angle), but without reducing the size of the image.

• what is already happening, saving the shaded area as a smaller image
• - this is what I would like, the dashed line is the new image size.

The server has PHP 5.3+. Links, code and explanations are very welcome.

Answer 1

This is not a complete answer, but I would take four corners, since the coordinates rotated them in your angle, and then calculated a new bounding box depending on the degree of the new coordinates. (assuming coordinates with a start in the lower left corner).

corners = rotate_each ( [(left,top) (left,bottom), (right,top), (right,bottom)], angle) new_bb_left = min([corners[0].x, corners[1].x, corners[2].x, corners[3].x]) new_bb_right = max([corners[0].x, corners[1].x, corners[2].x, corners[3].x]) new_bb_bottom = min([corners[0].y, corners[1].y, corners[2].y, corners[3].y]) new_bb_top = max([corners[0].y, corners[1].y, corners[2].y, corners[3].y]) 

Answer 2

This may be the way to do it. Calculate the width of the diagonal.

PHP has a square root function: http://se2.php.net/manual/en/function.sqrt.php So you must have a diagonal width that you could apply on the converted image.

Answer 3

There are many solutions, including trigonometric formulas, but this library seems to be a shortcut.

http://wideimage.sourceforge.net/

Example: http://wideimage.sourceforge.net/wp-content/current/demo/index.php?demo=rotate&output=preset%20for%20demo&colors=255&dither=1&match_palette=1