Read and rotate transparent or intransparent image

Read and rotate transparent or intransparent image. Output is the rotated image as RGB data and the transparency data alpha. No toolbox!

Rotateim.m

This function reads an (transparent) image and rotates it by theta degrees.

Features

• No toolbox required
• Read and rotate transparent/intransparent image
• Scale image size up/down
• Crop

Syntax

[imR,alphaR] = rotim(im,theta,bgColor,crop,scale,interpMethod)

INPUT:

im: a) image file name

b) struct with two fields, im.rgb image and im.alpha

im.rgb: height * width * (1 or 3), either 0-255 uint8 or 0-1 double

im.alpha: height * width, either 0-255 uint8 or 0-1 double

theta: Amount of rotation in degrees

bgColor: Color of the given background.

Optional, place holder: NaN

Default: [128, 128, 128]

Integer numbers in the range 0-255

Example: [255 255 0] for yellow

Color of some pixels at the opaque border of the rotated small image.

Those pixels come up by rotating the small image, especially visible with very small

images.

Perfect result is when S.’bgColor’ is the same RGB color as the background.

crop: crop image. Optional, default: no crop

true: crop transparent areas

false: no crop, default

scale: a scalar factor that scales (shrinks or enlarges) the image. Optional, default=1, no scaling

No antialiasing is invoked by changing the scale

interpMethod:

'nearest' - nearest neighbor interpolation, sometimes better for very small images

'linear' - bilinear interpolation (default), recommended

'cubic' - bicubic interpolation

OUTPUT:

imR: Rotated image as RGB values

alphaR: Rotated transparency

Remark:

To increase speed at multiple calls of rotim, some data is stored as peristent data.

Therefore, when the image content has changed, but not the image name, call

imrot without any argument to reset persistent data.

Example:

imshow(rotim('corn.tif',33))

See also enclosed "readMeRotateIm.pd"'.