Cropping, Resizing and Rescaling

This demonstration shows how to use cropping, resizing and rescaling operations on an image in Julia using ImageTransformations.jl

using Images, TestImages, OffsetArrays
# ImageTransformations is reexported by Images
# load an example image
img_source = testimage("lighthouse")

Cropping Operation

Cropping is one of the most basic photo manipulation processes, and it is carried out to remove an unwanted object or irrelevant noise from the periphery of a photograph, to change its aspect ratio, or to improve the overall composition.

Let's first check the size of the image

img_size = size(img_source)

(512, 768)

Output is (512,768) which stands means img_source is 512 in height and 768 in width. In Julia, images as multidimensional arrays are stored in column-major order, which means that this first index corresponds to the vertical axis (column) and the second to the horizontal axis (row).

Let's crop the image from sides by 1/8 of img_source each side and leave it as it is from top to bottom.

Easiest way to do this is indexing: img_source[y1:y2, x1:x2]

Region of Interest: [y1, y2] sets the range for y-axis and [x1, x2] sets the range for x-axis of source image.

img_cropped = @view img_source[ :,floor(Int, 1/8*img_size[2]) : floor(Int, 7/8*img_size[2])]