ios - 类型 'UnsafeMutableRawPointer' 的值没有下标 Swift 5

Question

我正在尝试将 Objective C 代码转换为 swift。

UInt8* data = calloc(bytesPerRow, height);

当我快速转换它时，它返回“UnsafeMutableRawPointer”。我需要 UInt8。

let data = calloc(bytesPerRow, height)! // UnsafeMutableRawPointer

我尝试了不同的解决方案，但对我不起作用。谁能告诉我如何解决这个问题。谢谢

Value of type 'UnsafeMutableRawPointer' has no subscripts

Swift 代码。

 // data pointer – stores an array of the pixel components. For example (r0, b0, g0, a0, r1, g1, b1, a1 .... rn, gn, bn, an)
        //*calloc(size_t __count, size_t __size) __result_use_check __alloc_size(1,2);
        let data = calloc(bytesPerRow, height)!

        // get new RGB color space
        let colorSpace = CGColorSpaceCreateDeviceRGB()

        // create bitmap context
        let ctx = CGContext(data: data, width: width, height: height, bitsPerComponent: bitsPerComponent, bytesPerRow: bytesPerRow, space: colorSpace, bitmapInfo: bitmapInfo.rawValue)

        // draw image into context (populating the data array while doing so)
        ctx?.draw(rawImage!, in: rect)

        // get the index of the pixel (4 components times the x position plus the y position times the row width)
        var pixelIndex = 4 * (pixelPosition.x + (pixelPosition.y * width))

        // set the pixel components to the color components
        data[pixelIndex] = color255Components[0]; // r
        data[pixelIndex+1] = color255Components[1]; // g
        data[pixelIndex+2] = color255Components[2]; // b
        data[pixelIndex+3] = color255Components[3]; // a

Objective-C 代码。

// data pointer – stores an array of the pixel components. For example (r0, b0, g0, a0, r1, g1, b1, a1 .... rn, gn, bn, an)
    UInt8* data = calloc(bytesPerRow, height);

    // get new RGB color space
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();

    // create bitmap context
    CGContextRef ctx = CGBitmapContextCreate(data, width, height, bitsPerComponent, bytesPerRow, colorSpace, bitmapInfo);

    // draw image into context (populating the data array while doing so)
    CGContextDrawImage(ctx, rect, rawImage);

    // get the index of the pixel (4 components times the x position plus the y position times the row width)
    NSInteger pixelIndex = 4*(pixelPosition.x+(pixelPosition.y*width));

    // set the pixel components to the color components
    data[pixelIndex] = color255Components[0]; // r
    data[pixelIndex+1] = color255Components[1]; // g
    data[pixelIndex+2] = color255Components[2]; // b
    data[pixelIndex+3] = color255Components[3]; // a

Answer 1

您需要为可变指针分配一个类型。在当前状态下，它是一个指向任何内容的可变指针，但您希望它是一个指向 UInt8 值缓冲区的可变指针。

为此，只需对您的数据调用 assumeMemoryBound 即可:

let data = calloc(bytesPerRow, height)!.assumingMemoryBound(to: UInt8.self)