Arithmetic Exception Swift

Question

currently I am trying to create an App with Particle effects to match an image. When doing so I am frequently running into Arithmetic Exceptions when trying to read the image and process it in especially this method.

func getPixels() -> [[Int]] {
        guard let cgImage = self.cgImage,
              let data = cgImage.dataProvider?.data,
              let bytes = CFDataGetBytePtr(data) else {
            fatalError("Couldn't access image data")
        }
        var pixelMap = repeatElement(repeatElement(0, count: cgImage.height).map { $0 }, count: cgImage.width).map { $0 }
        let bytesPerPixel = cgImage.bitsPerPixel / cgImage.bitsPerComponent
        for y in 0 ..< cgImage.height {
            for x in 0 ..< cgImage.width {
                let offset = (y * cgImage.bytesPerRow) + (x * bytesPerPixel)
                let components = (r: bytes[offset], g: bytes[offset + 1], b: bytes[offset + 2])
                pixelMap[x][y] = Int((components.r + components.g + components.b)/3)
            }
            
        }
        
        return pixelMap
    }

In this line pixelMap[x][y] = Int((components.r + components.g + components.b)/3), I frequently get an Arithmetic Overflow and wanted to know if there is any possible way to resolve this error. I would assume that the full number couldn't be stored, but is there any way to store such a number, perhaps in a combination of integers? If so, how could I possibly implement that here?

Full source code can be found here, if desired: https://github.com/Alpheron/Particles

Answer 1

To convert MartinR's comment into code, the change would be here:

// First convert all the values to Int
let components = (r: Int(bytes[offset]), g: Int(bytes[offset + 1]), b: Int(bytes[offset + 2]))

// Then perform computations within the Int range.
// There's no need to convert at the end.
pixelMap[x][y] = (components.r + components.g + components.b)/3

This causes the + to operate on Int values rather than UInt8, ensuring there's sufficient range to perform the addition without overflowing.