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本案例的目的是理解如何用Metal实现图像单色效果滤镜，将图像转换为单色版本，根据每个像素的亮度进行着色；
Demo
实操代码
// 去雾效果滤镜
let filter = C7Monochrome.init(intensity: 0.83, color: .blue)
// 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
| intensity: 0.25, color: .blue | intensity: 0.5, color: .blue | intensity: 0.83, color: .blue |
|---|---|---|
| intensity: 0.5, color: .yellow | intensity: 0.5, color: .red | intensity: 0.5, color: .green |
|---|---|---|
实现原理
- 过滤器
这款滤镜采用并行计算编码器设计.compute(kernel: "C7Monochrome")，参数因子[intensity] + RGBAColor(color: color).toRGB()；
对外开放参数
intensity: 特定颜色取代正常图像颜色的程度，从0.0到1.0，默认值为0.0；color: 保留配色方案；
/// 将图像转换为单色版本，根据每个像素的亮度进行着色
public struct C7Monochrome: C7FilterProtocol {
public static let range: ParameterRange<Float, Self> = .init(min: 0.0, max: 1.0, value: 0.0)
/// The degree to which the specific color replaces the normal image color, from 0.0 to 1.0, with 0.0 as the default.
@ZeroOneRange public var intensity: Float = range.value
/// Keep the color scheme
public var color: C7Color = .zero
public var modifier: Modifier {
return .compute(kernel: "C7Monochrome")
}
public var factors: [Float] {
return [intensity] + RGBAColor(color: color).toRGB()
}
public init(intensity: Float = range.value, color: C7Color = .zero) {
self.intensity = intensity
self.color = color
}
}
- 着色器
获取像素亮度值dot(inColor.rgb, luminanceWeighting)，然后混合强度intensity原始像素和单色值三者获取新的像素颜色rgb；
kernel void C7Monochrome(texture2d<half, access::write> outputTexture [[texture(0)]],
texture2d<half, access::read> inputTexture [[texture(1)]],
constant float *intensity [[buffer(0)]],
constant float *colorR [[buffer(1)]],
constant float *colorG [[buffer(2)]],
constant float *colorB [[buffer(3)]],
uint2 grid [[thread_position_in_grid]]) {
const half4 inColor = inputTexture.read(grid);
const half3 luminanceWeighting = half3(0.2125, 0.7154, 0.0721);
const half luminance = dot(inColor.rgb, luminanceWeighting);
const half4 desat = half4(half3(luminance), 1.0h);
const half r = desat.r < 0.5 ? (2.0 * desat.r * half(*colorR)) : (1.0 - 2.0 * (1.0 - desat.r) * (1.0 - half(*colorR)));
const half g = desat.g < 0.5 ? (2.0 * desat.g * half(*colorG)) : (1.0 - 2.0 * (1.0 - desat.g) * (1.0 - half(*colorG)));
const half b = desat.b < 0.5 ? (2.0 * desat.b * half(*colorB)) : (1.0 - 2.0 * (1.0 - desat.b) * (1.0 - half(*colorB)));
const half4 outColor = half4(mix(inColor.rgb, half3(r, g, b), half(*intensity)), inColor.a);
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。
✌️.
