这段代码是什么意思？ OpenCV的

May I know what does x represent? Does the content inside of () represent a pointer? then the [] is the element of the array?

我可以知道x代表什么？ （）内的内容是否代表指针？那么[]是数组的元素？

 x = (df_dx->imageData+i*df_dx->widthStep)[j]; 

why doesnt it work if i put it this way?

如果我这样说，为什么它不起作用？

 x=df_dx[2][j];

Does the

是吗？

->imageData

give the pixel value of the image? The full code is below. THanks

给出图像的像素值？完整代码如下。谢谢

float x;
IplImage*df_dx = cvCreateImage(cvGetSize(grayimg),IPL_DEPTH_16S,1); 


for(int i=0;i=grayimg->height;i++)
{
for(int j=0;grayimg->width;j++)
{

x = (df_dx->imageData+i*df_dx->widthStep)[j]; 
}
}

1 个解决方案

#1

Short answers:

简短的答案：

• x is the element on row j, column i of the matrix df_dx
• x是矩阵df_dx的第j行第i列的元素
• df_dx->imageData returns a pointer to the first element of the array (top-left)
• df_dx-> imageData返回指向数组第一个元素的指针（左上角）

Accessing matrix elements in such a way is actually quite common for 2d matrices stored in memory as flat one-dimensional arrays (see e.g. GSL matrix accesses for a similar example with another library; see also this post for a similar question).

以这种方式访问​​矩阵元素实际上对于存储在存储器中的2d矩阵作为平坦的一维阵列是很常见的（参见例如对于具有另一个库的类似示例的GSL矩阵访问;也参见该帖子以获得类似的问题）。

Storing a matrix as an array of arrays (i.e. using [][] for access) is definitely manageable, and many people chose to use this representation, but there are reasons why one would prefer a flat layout in memory.

将矩阵存储为数组数组（即使用[] []进行访问）绝对是可管理的，并且许多人选择使用此表示，但有理由为什么人们更喜欢内存中的平面布局。