iOS 在 UIView 中绘制像素

Question

我有一个 RGB 值的二维数组(或任何此类数据容器)，我需要将其写入当前显示给用户的 UIView。一个例子是——在使用相机的捕获输出时，我运行一些算法来识别对象，然后使用自定义的 RGB 像素突出显示它们。

做这件事的最佳方法是什么，例如，整个过程是每秒 10 帧实时完成的？

Answer 1

使用下面的方法从您的二维数组创建一个 UIImage。然后，您可以使用 UIImageView 显示此图像。

-(UIImage *)imageFromArray:(void *)array width:(unsigned int)width height:(unsigned int)height {
    /*
     Assuming pixel color values are 8 bit unsigned

     You need to create an array that is in the format BGRA (blue,green,red,alpha).  
     You can achieve this by implementing a for-loop that sets the values at each index. 
     I have not included a for-loop in this example because it depends on how the values are stored in your input 2D array.  
     You can set the alpha value to 255.
    */
    unsigned char pixelData[width * height * 4];

    // This is where the for-loop would be

    void *baseAddress = &pixelData;

    size_t bytesPerRow = width * 4;

    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    CGContextRef context = CGBitmapContextCreate(baseAddress, width, height, 8, bytesPerRow, colorSpace, kCGBitmapByteOrder32Little | kCGImageAlphaPremultipliedFirst);

    CGImageRef cgImage = CGBitmapContextCreateImage(context);
    UIImage *image = [UIImage imageWithCGImage:cgImage];

    CGImageRelease(cgImage);
    CGColorSpaceRelease(colorSpace);
    CGContextRelease(context);

    return image;
}