无法从'ref byte []'转换为'ref object' [英] cannot convert from 'ref byte[]' to 'ref object'

问题描述

我尝试读取图像中某一行的像素值：

I try to read the pixels value on a line in an image:

byte[] myArray=new byte[20];
for(int i=0;i<20;i++)
    myArray[i]=0;

myImage.GetLine(ref myArray, 10,10,20,10);

Getline是myImage提供的函数，它有5个参数：

ref对象，int startX，int startY，int endX， int EndY;



运行上面的代码时，它会显示错误：无法将'ref byte []'转换为'ref object'。



但是当我用这种方式调用它时：

Getline is the function provided by myImage, which has 5 parameters:
ref object, int startX,int startY, int endX,int EndY;

When run the above code, it will show error as: cannot convert 'ref byte[]' to 'ref object'.

But when I call it in this way:

object points=null;
myImage.GetLine(ref points,10,10,20,10);
The error will show as: invalid userarray.

不知道为什么？

Don't know why?

推荐答案

你不能用ref参数调用方法到 以外的任何类型 指定的参数类型。推理非常简单 - 假设你可以：

You cannot call the method with a ref parameter to any type other than exactly the parameter type specified. The reasoning is pretty simple - suppose you could:

private void MyMethod(ref object o)
   {
   o = (object) new Point(10, 10);
   }
...
   byte[] data = new byte[1024];
   MyMethod(ref data);
   Console.WriteLine(data[100]);

你会得到什么样的输出？除了随机和垃圾？



为了使用ref参数调用方法，它必须是 可分配 值，所以请尝试

What kind of output would you get? Apart from random and rubbish?

In order to call a method with a ref parameter, it must be an assignable value, so try

byte[] myArray=new byte[20];
for(int i=0;i<20;i++)
    myArray[i]=0;
object o = myArray;
myImage.GetLine(ref o, 10,10,20,10);

该方法可以然后更改o的值而不会以任何方式影响数组。

The method can then change the value of o without affecting the array in any way.

似乎需要从myArray到Object的强制转换。

我想得到的是鼠标在图像上移动时获取像素值。



谢谢。我稍后会试一试。

Seems it will need a cast from myArray to Object.
What I want to get is to get a pixel's value when mouse moved on an image.

Thank you. I will try this later.

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