Metal学习（三）- 图像拉伸问题

在上一篇(视频播放)中，如果放入的视频不是16:9, 会发现图像的形状会被拉伸，要解决这个问题只需要修改顶点数据就可以了。

上代码

...
let wY = CVPixelBufferGetWidthOfPlane(pixelBuffer, 0)
let hY = CVPixelBufferGetHeightOfPlane(pixelBuffer, 0)
let vs = transformVertices(vertex: vertexs, inputSize: CGSize(width: wY, height: hY), drawableSize: mtkView.drawableSize)
let vertexBuffer = device.makeBuffer(bytes: vs, length: MemoryLayout.size * 8, options: [])
let textureVerBuffer = device.makeBuffer(bytes: textureCoordinates, length: MemoryLayout.size * 8, options: [])
renderCommandEncoder.setVertexBuffer(vertexBuffer, offset: 0, index: 0)
renderCommandEncoder.setVertexBuffer(textureVerBuffer, offset: 0, index: 1)
...

/// 顶点转换
    func transformVertices(vertex: [Float], inputSize: CGSize, drawableSize: CGSize) -> [Float] {
        
        let inputAspectRatio = inputSize.height / inputSize.width
        let drawableAspectRatio = drawableSize.height / drawableSize.width
        
        var xRatio: Float = 1.0
        var yRatio: Float = 1.0
        
        if inputAspectRatio > drawableAspectRatio {
            yRatio = 1.0
            xRatio = Float((inputSize.width / drawableSize.width) * (drawableSize.height / inputSize.height))
        }else {
            xRatio = 1.0
            yRatio = Float((inputSize.height / drawableSize.height) * (drawableSize.width / inputSize.width))
        }
        
        let value1 = vertex[0] * xRatio
        let value2 = vertex[1] * yRatio
        
        let value3 = vertex[2] * xRatio
        let value4 = vertex[3] * yRatio
        
        let value5 = vertex[4] * xRatio
        let value6 = vertex[5] * yRatio
        
        let value7 = vertex[6] * xRatio
        let value8 = vertex[7] * yRatio
        
        return [value1, value2, value3, value4, value5, value6, value7, value8]
    }

经过转换之后，就可以正常的显示图像，如下：

IMG_0066.PNG

具体实现已经更新到Metal-10(视频播放)中。