From a1deb6cac305a73e799c63e2fbfe7221790e1e61 Mon Sep 17 00:00:00 2001 From: Eli Zaretskii Date: Sun, 23 Jun 2019 19:24:32 +0300 Subject: [PATCH] ; * src/image.c: Minor copyedits of native transform commentary. --- src/image.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/src/image.c b/src/image.c index 866323ba6e5..7b648c46ae9 100644 --- a/src/image.c +++ b/src/image.c @@ -1986,7 +1986,7 @@ compute_image_size (size_t width, size_t height, Transforms are done by creating a matrix for each action we wish to take, then multiplying the transformation matrix by each of those matrices in order (matrix multiplication is not commutative). - After we’ve done that we can use our modified transformation matrix + After we've done that we can use our modified transformation matrix to transform points. We take the x and y coordinates and convert them into a 3x1 matrix and multiply that by the transformation matrix and it gives us a new, transformed, set of coordinates: @@ -1995,7 +1995,7 @@ compute_image_size (size_t width, size_t height, [m21 m22 ty] X [y] = [m21*x+m22*y+ty*1] = [y'] [ 0 0 1] [1] [ 0*x+0*y+1*1] [ 1] - We don’t have to worry about the last step as the graphics toolkit + We don't have to worry about the last step as the graphics toolkit will do it for us. The three transforms we are concerned with are translation, scaling @@ -2029,19 +2029,19 @@ compute_image_size (size_t width, size_t height, [ 0 0 1] Where r is the angle of rotation required. Rotation occurs around - the origin, not the centre of the image. Note that this is + the origin, not the center of the image. Note that this is normally considered a counter-clockwise rotation, however because our y axis is reversed, (0, 0) at the top left, it works as a clockwise rotation. The full process of rotating an image is to move the origin to the - centre of the image (width/2, height/2), perform the rotation, and + center of the image (width/2, height/2), perform the rotation, and finally move the origin back to the top left of the image, which may now be a different corner. Cropping is easier as we just move the origin to the top left of where we want to crop and set the width and height accordingly. - The matrices don’t know anything about width and height. + The matrices don't know anything about width and height. It's possible to pre-calculate the matrix multiplications and just generate one transform matrix that will do everything we need in a -- 2.39.5