I'm learning how to write custom Core Image filters, but have this problem where the rendered color is not the same as specified in kernel code when color value is between 0 - 1. (Color is correct when equal to 0 or 1.)
This is my filter code:
import UIKit
class testFilter: CIFilter
{
// simply return half red color (0.5)
var colorKernel = CIColorKernel(string:
"kernel vec4 theFilter()" +
"{ return vec4(0.5, 0.0, 0.0, 1.0); }"
)
override var outputImage: CIImage!
{
let rect = CGRect(x: 0, y: 0, width: 200, height: 100)
return colorKernel.applyWithExtent(rect,arguments: nil)
}
}
Usage:
class ViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
// generate image
let filter = testFilter()
let ciImage = f.outputImage
let image = UIImage(CIImage: ciImage)
// add to view
let v = UIImageView(frame: CGRect(x: 50, y: 50, width: 200, height: 100))
v.image = image
view.addSubview(v)
}
}
The output image looks like this, the actual red component value is around 190 (I checked color value using Photoshop). For a value of 0.5 I thought the correct output value would be 255 * 0.5 = 122.5?
from Custom Core Image filter color issue
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