         return nil
     }
     
+    func pixelChange(variable: String, stringLiteral: String) throws -> String? {
+        if get(variable) == nil {
+            print("Tried to change pixels of a null image")
+            throw ExecErrors.NullPointerError
+        }
+        if !stringLiteral.containsString("->") {
+            print("The syntax of replaceColors is 'var.replaceColors(COLOR1->COLOR2)'")
+            throw ExecErrors.SyntaxError
+        }
+        let cmps = stringLiteral.componentsSeparatedByString("->")
+        try set(variable, value: UIImagePNGRepresentation(pixelChangeImpl(getImage(variable).CGImage!, from: parseColor(cmps[0]), to: parseColor(cmps[1])))!.base64EncodedStringWithOptions(.Encoding64CharacterLineLength))
+        return nil
+    }
+    
+    /// SO: 27092354
     func rotateImpl(image: UIImage, radians: CGFloat, flip: Bool) -> UIImage {
         let rotatedViewBox = UIView(frame: CGRect(origin: CGPointZero, size: image.size))
         rotatedViewBox.transform = CGAffineTransformMakeRotation(radians)

        case NullPointerError
        case EditConstantError
    }
}
//

import Foundation
import SpriteKit

class BBT2 {
    let null:String? = nil
