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本案例的目的是理解如何用Metal实现去雾效果滤镜，类似于UV过滤器；
Demo
实操代码
// 去雾效果滤镜
let filter = C7Haze.init(distance: 0.5, slope: 0.5)
// 方案1:
ImageView.image = try? BoxxIO(element: originImage, filters: [filter, filter2, filter3]).output()
// 方案2:
ImageView.image = originImage.filtering(filter, filter2, filter3)
// 方案3:
ImageView.image = originImage ->> filter ->> filter2 ->> filter3
效果对比图
- 不同参数下效果
| distance: 0.25, slope: 0.25 | distance: 0.25, slope: 0.5 | distance: 0.4, slope: 0.5 |
|---|---|---|
实现原理
- 过滤器
这款滤镜采用并行计算编码器设计.compute(kernel: "C7Haze")，参数因子[distance, slope]；
对外开放参数
distance: 应用颜色的强度；slope: 颜色变化量；
/// 去雾，类似于UV过滤器
public struct C7Haze: C7FilterProtocol {
/// Strength of the color applied.
public var distance: Float = 0
/// Amount of color change.
public var slope: Float = 0
public var modifier: Modifier {
return .compute(kernel: "C7Haze")
}
public var factors: [Float] {
return [distance, slope]
}
public init(distance: Float = 0, slope: Float = 0) {
self.distance = distance
self.slope = slope
}
}
- 着色器
归一化y乘以颜色变化量，加上强度，得到像素颜色(inColor - dd * white) / (1.0h - dd)；
kernel void C7Haze(texture2d<half, access::write> outputTexture [[texture(0)]],
texture2d<half, access::read> inputTexture [[texture(1)]],
constant float *hazeDistance [[buffer(0)]],
constant float *slope [[buffer(1)]],
uint2 grid [[thread_position_in_grid]]) {
const half4 inColor = inputTexture.read(grid);
const half4 white = half4(1.0h);
const half dd = half(grid.y) / half(inputTexture.get_height()) * half(*slope) + half(*hazeDistance);
const half4 outColor = half4((inColor - dd * white) / (1.0h - dd));
outputTexture.write(outColor, grid);
}
最后
- 慢慢再补充其他相关滤镜，喜欢就给我点个星🌟吧。
✌️.
