byte_shrink_1x2 src dest
byte_shrink_2x1 src dest
byte_shrink_2x2 src dest
byte_shrink_4x4 src dest
ByteShrinkMxN shrinks src by a factor of M
in the horizontal direction and N in the vertical direction.
The result is written into dest. Pixels are combined
by averaging (i.e., a box filter is used). Upon return,
newWidth and newHeight contain the width and
height of the resulting image.
For example, to scale a 320x240 image down to 160x120, you would
use ByteShrink2x2(). ByteShrink1x2() would scale the
same image to 320x120. These functions return a list containing the new width and
height of the resulting image.
byte_expand_4x4 src dest
byte_expand_2x2 src dest
byte_expand_1x2 src dest
byte_expand_2x1 src dest
ByteExpandMxN enlarges src by a factor of M
in the horizontal direction and N in the vertical direction.
The result is written into dest. Pixels are combined
by duplication (i.e., the effect is one of "fat-bitting" the pixels)
Upon return, newWidth and newHeight contain the
width and height of the resulting image.
For example, to scale a 80x60 image up to 320x240, you would
use ByteExpand4x4(). These functions return a list containing the new width and
height of the resulting image.
byte_scale_bilinear src dest newWidth newHeight
Scale src to fit into an area newWidth x
newHeight pixels in dest using bilinear
interpolation. The result is written into starting at the upper
left corner of dest.
For best results, the overall scaling factor should be between 1/2 and 2.
ByteScaleBilinear will produce reasonable results for other
factors, but some aliasing may occur.
For scaling up or down by more than a factor of two, you should apply
ByteShrinkMxN or ByteExpandMxN until the scaling factor
is within between 1/2 and 2. Nothing is returned if the operations is successful, otherwise an error is thrown.
byte_rotate_90a src dest
byte_rotate_90c src dest
ByteRotate90a rotates src anti-clockwise by 90 degrees and stores the
result in dest.
ByteRotate90c rotates src clockwise by 90 degrees.
byte_rotate_orig src dest theta
This function rotates src counter-clockwise by
theta degrees around its origin (i.e., the top-left
corner of src). The rotated image is stored in
dest.
byte_rotate src dest theta x y
This function rotates src counter-clockwise by
theta degrees around the point (x,y).
The rotated image is stored in dest.
byte_affine src dest a b c d e f
Texture map src using the affine transformation
specified by the parameters a..f. The result is
written into dest.
The equation of the transform is
x' = ax + by + c
y' = dx + ey + f
where (x,y) are coordinates in src, and (x',y') are
coordinates in dest.
byte_affine_rect_region src a b c d e f
Return the bounding box that src will map to (in the coordinate
system of dest) given the affine coefficients specified. The return value is a list of four numbers, {x y w h}, which
give the upper left corner (x,y) and the width and
height (w,h) of the box.
byte_homo src dest a b c d e f m n p
Texture map src using the homogeneous transformation
specified by the floating point parameters a..p.
The result is written into dest.
The equation of the transform is
x' = (ax+by+c) / w
y' = (dx+ey+f) / w
where
The coordinates (x,y) are in src, and (x',y') are
in the dest.
Note: this function assumes that dest is large enough
to accomodate the transformed image. It may cause a segmentation
fault otherwise.
byte_homo_rect_region src a b c d e f m n p
Return the bounding box (in destination image coordinates) where
src will be mapped if it is texture mapped using the given
homogeneous matrix coefficients. The return value is a list of
four numbers, {x y w h}, which give the upper left
corner (x,y) and the width and height (w,h) of the box
in the coordinate system of the destination image.
byte_homo_compute_matrix w h x1 y1 x2 y2 x3 y3
Find the homogeneous matrix which transforms the rectangle with
corners at (0,0), (w,0), (w,h), (0,h) into the the quadrilateral
with coordinates (0,0), (x1,y1), (x2,y2) (x3,y3)
The return value is a list of six floating point numbers,
{a b d e m n}, in the matrix
a b 0
d e 0
m n 1
An error is generated if no projective transform exists given
the value specified.
byte_homo_invert_matrix a b d e m n
a b 0
d e 0
m n 1
The return value is a list of six floating point numbers numbers,
{a' b' d' e' m' n'} in the matrix
a' b' 0
d' e' 0
m' n' 1
An error is generated if the matrix passed has no inverse