Binary operator '+=' cannot be applied to operands of type 'Int' and 'UInt8' - objective-c

Question

Translating Obj-C to Swift. As you can see I declared let buf = UnsafeMutablePointer<UInt8>(CVPixelBufferGetBaseAddress(cvimgRef)) so I'm getting the error in the for loop below it.
Binary operator '+=' cannot be applied to operands of type 'Int' and 'UInt8'
Also as a little addendum I don't know how to translate the remaining Obj-C code below the for loop. What does that slash mean and how do I deal with the pointer? I have to say UnsafeMutableFloat somewhere?
// process the frame of video
func captureOutput(captureOutput:AVCaptureOutput, didOutputSampleBuffer sampleBuffer:CMSampleBuffer, fromConnection connection:AVCaptureConnection) {
// if we're paused don't do anything
if currentState == CurrentState.statePaused {
// reset our frame counter
self.validFrameCounter = 0
return
}
// this is the image buffer
var cvimgRef:CVImageBufferRef = CMSampleBufferGetImageBuffer(sampleBuffer)
// Lock the image buffer
CVPixelBufferLockBaseAddress(cvimgRef, 0)
// access the data
var width: size_t = CVPixelBufferGetWidth(cvimgRef)
var height:size_t = CVPixelBufferGetHeight(cvimgRef)
// get the raw image bytes
let buf = UnsafeMutablePointer<UInt8>(CVPixelBufferGetBaseAddress(cvimgRef))
var bprow: size_t = CVPixelBufferGetBytesPerRow(cvimgRef)
var r = 0
var g = 0
var b = 0
for var y = 0; y < height; y++ {
for var x = 0; x < width * 4; x += 4 {
b += buf[x]; g += buf[x + 1]; r += buf[x + 2] // error
}
buf += bprow() // error
}
Remaining Obj-C code.
r/=255*(float) (width*height);
g/=255*(float) (width*height);
b/=255*(float) (width*height);

Answer 1

You have a lot of type mismatch error.
The type of x should not be UInt8 because x to increase until the value of the width.
for var x:UInt8 = 0; x < width * 4; x += 4 { // error: '<' cannot be applied to operands of type 'UInt8' and 'Int'
So fix it like below:
for var x = 0; x < width * 4; x += 4 {
To increment the pointer address, you can use advancedBy() function.
buf += bprow(UnsafeMutablePointer(UInt8)) // error: '+=' cannot be applied to operands of type 'UnsafeMutablePointer<UInt8>' and 'size_t'
Like below:
var pixel = buf.advancedBy(y * bprow)
And this line,
RGBtoHSV(r, g, b) // error
There are no implicit casts in Swift between CGFloat and Float unfortunately. So you should cast explicitly to CGFloat.
RGBtoHSV(CGFloat(r), g: CGFloat(g), b: CGFloat(b))
The whole edited code is here:
func RGBtoHSV(r: CGFloat, g: CGFloat, b: CGFloat) -> (h: CGFloat, s: CGFloat, v: CGFloat) {
var h: CGFloat = 0.0
var s: CGFloat = 0.0
var v: CGFloat = 0.0
let col = UIColor(red: r, green: g, blue: b, alpha: 1.0)
col.getHue(&h, saturation: &s, brightness: &v, alpha: nil)
return (h, s, v)
}
// process the frame of video
func captureOutput(captureOutput:AVCaptureOutput, didOutputSampleBuffer sampleBuffer:CMSampleBuffer, fromConnection connection:AVCaptureConnection) {
// if we're paused don't do anything
if currentState == CurrentState.statePaused {
// reset our frame counter
self.validFrameCounter = 0
return
}
// this is the image buffer
var cvimgRef = CMSampleBufferGetImageBuffer(sampleBuffer)
// Lock the image buffer
CVPixelBufferLockBaseAddress(cvimgRef, 0)
// access the data
var width = CVPixelBufferGetWidth(cvimgRef)
var height = CVPixelBufferGetHeight(cvimgRef)
// get the raw image bytes
let buf = UnsafeMutablePointer<UInt8>(CVPixelBufferGetBaseAddress(cvimgRef))
var bprow = CVPixelBufferGetBytesPerRow(cvimgRef)
var r: Float = 0.0
var g: Float = 0.0
var b: Float = 0.0
for var y = 0; y < height; y++ {
var pixel = buf.advancedBy(y * bprow)
for var x = 0; x < width * 4; x += 4 { // error: '<' cannot be applied to operands of type 'UInt8' and 'Int'
b += Float(pixel[x])
g += Float(pixel[x + 1])
r += Float(pixel[x + 2])
}
}
r /= 255 * Float(width * height)
g /= 255 * Float(width * height)
b /= 255 * Float(width * height)
//}
// convert from rgb to hsv colourspace
var h: Float = 0.0
var s: Float = 0.0
var v: Float = 0.0
RGBtoHSV(CGFloat(r), g: CGFloat(g), b: CGFloat(b)) // error
}