objective c - Using sprite sheets in xcode

Question

I'm trying to animate my game using a sprite sheet. How would I go about cutting out each sprite from the sprite sheet and using the sprite in xcode? I'm currently using obj -c. I read somewhere that i need to use a frame work, cocoa2d, in order to do this?

Answer 1

In sprite kit you can cut part of a texture out using SKTexture(rect: inTexture:) initializer. This is a helper class which manages an evenly spaced sprite sheet and can cut out a texture at a given row and column. It is used like So

let sheet=SpriteSheet(texture: SKTexture(imageNamed: "spritesheet"), rows: 1, columns: 11, spacing: 1, margin: 1)
let sprite=SKSpriteNode(texture: sheet.textureForColumn(0, row: 0))

Here is the full code

//
//  SpriteSheet.swift
//

import SpriteKit

class SpriteSheet {
    let texture: SKTexture
    let rows: Int
    let columns: Int
    var margin: CGFloat=0
    var spacing: CGFloat=0
    var frameSize: CGSize {
        return CGSize(width: (self.texture.size().width-(self.margin*2+self.spacing*CGFloat(self.columns-1)))/CGFloat(self.columns),
            height: (self.texture.size().height-(self.margin*2+self.spacing*CGFloat(self.rows-1)))/CGFloat(self.rows))
    }

    init(texture: SKTexture, rows: Int, columns: Int, spacing: CGFloat, margin: CGFloat) {
        self.texture=texture
        self.rows=rows
        self.columns=columns
        self.spacing=spacing
        self.margin=margin

    }

    convenience init(texture: SKTexture, rows: Int, columns: Int) {
        self.init(texture: texture, rows: rows, columns: columns, spacing: 0, margin: 0)
    }

    func textureForColumn(column: Int, row: Int)->SKTexture? {
        if !(0...self.rows ~= row && 0...self.columns ~= column) {
            //location is out of bounds
            return nil
        }

        var textureRect=CGRect(x: self.margin+CGFloat(column)*(self.frameSize.width+self.spacing)-self.spacing,
                               y: self.margin+CGFloat(row)*(self.frameSize.height+self.spacing)-self.spacing,
                               width: self.frameSize.width,
                               height: self.frameSize.height)

        textureRect=CGRect(x: textureRect.origin.x/self.texture.size().width, y: textureRect.origin.y/self.texture.size().height,
            width: textureRect.size.width/self.texture.size().width, height: textureRect.size.height/self.texture.size().height)
        return SKTexture(rect: textureRect, inTexture: self.texture)
    }

}

The margin property is the gap between the edge of the image and the sprites. The spacing is the gap between each sprite. The fameSize is the size each sprite will be. This image explains it: