iOS Picture Cropping + Rotation

Before, we introduced the methods of picture cropping and picture rotation respectively

[iOS Picture Cropping Method]

Address: https://www.ofstack.com/article/107308. htm

"iOS Image Rotation Method"

Address: https://www.ofstack.com/article/107361. htm

Cropping and rotation can be performed in one place. First, locate the area to be clipped, then take the center of this area as the axis, rotate 1 fixed angle, and finally get the picture in this area after rotation. It can be realized by bitmap (Bitmap) drawing

static func cropImage(_ image: UIImage, withRect rect: CGRect, angle: Double) -> UIImage? {
 // Creates a bitmap-based graphics context with rect size
 // and makes it the current context
 UIGraphicsBeginImageContext(rect.size)
 // Get current graphics context
 guard let context = UIGraphicsGetCurrentContext() else { return nil }
 // Move context origin to rect center
 context.translateBy(x: rect.width / 2, y: rect.height / 2)
 // Convert angle to radian and rotate
 context.rotate(by: CGFloat(angle / 180 * M_PI))
 // Move context origin back (-rect.width / 2, -rect.height / 2)
 // and move opposite direction of rect origin (-rect.minX, -rect.minY)
 context.translateBy(x: -rect.width / 2 - rect.minX, y: -rect.height / 2 - rect.minY)
 // Draw image at context origin
 image.draw(at: .zero)
 // Get image
 let finalImage = UIGraphicsGetImageFromCurrentImageContext()
 // Removes the current bitmap-based graphics context from the top of the stack
 UIGraphicsEndImageContext()
 // Return image
 return finalImage
}

rect is the area that needs to be cut, and adopts the coordinate system of the original drawing. angle is the angle to be rotated in degrees, and a positive value indicates that the picture rotates clockwise. See the notes for the explanation of the specific implementation.

The final image may exceed the original image area, and the excess is transparent.