为什么我的图像旋转算法不起作用？ [英] Why is my image rotation algorithm not working?

问题描述

注意：删除了首次尝试减少问题大小。请参阅社区维基以了解之前的尝试。

Note: Removed first attempts to cut down on question size. See community wiki for previous attempts.

根据模糊华夫饼的例子，我已实施以下，似乎无法正常工作。任何想法我可能做错了吗？

As per fuzzy-waffle's example, I have implemented the following, which doesn't appear to work correctly. Any ideas what I could be doing wrong?

ImageMatrix ImageMatrix::GetRotatedCopy(VDouble angle)
{
    // Copy the specifications of the original.
    ImageMatrix &source = *this;
    ImageMatrix &target = CreateEmptyCopy();

    double centerX = ((double)(source.GetColumnCount()-1)) / 2;
    double centerY = ((double)(source.GetRowCount()-1)) / 2;

    // Remember: row = y, column = x
    for (VUInt32 y = 0; y < source.GetRowCount(); y++)
    {
        for (VUInt32 x = 0; x < source.GetColumnCount(); x++)
        {
            double dx = ((double)x) - centerX;
            double dy = ((double)y) - centerY;

            double newX = cos(angle) * dx - sin(angle) * dy + centerX;
            double newY = cos(angle) * dy + sin(angle) * dx + centerY;

            int ix = (int)round(newX);
            int iy = (int)round(newY);

            target[x][y][0] = source[ix][iy][0];
        }
    }

    return target;
}

使用此原型矩阵......

With this prototype matrix...

1 2 1 
0 0 0 
-1 -2 -1 

... prototype.GetRotatedCopy（0）（这是正确的）...

... prototype.GetRotatedCopy(0) (which is correct) ...

1 2 1 
0 0 0 
-1 -2 -1 

... prototype.GetRotatedCopy（90）（不正确）...

... prototype.GetRotatedCopy(90) (incorrect) ...

-2 0 0 
-2 0 2 
0 0 2 

... prototype.GetRotatedCopy（180） （不正确 - 但有点合乎逻辑？）...

... prototype.GetRotatedCopy(180) (incorrect - but sort of logical?) ...

0 -1 -2 
1 0 -1 
2 1 0 

... prototype.GetRotatedCopy（270）（不正确 - 这是为什么与0轮相同？）...

... prototype.GetRotatedCopy(270) (incorrect - why is this the same as 0 rotation?) ...

1 2 1 
0 0 0 
-1 -2 -1 

解决方案：

正如Mark Ransom所指出的，我应该使用弧度，而不是度数;我调整了我的代码如下：

Solution:

As pointed out by Mark Ransom, I should be using radians, not degrees; I have adjusted my code as follows:

ImageMatrix ImageMatrix::GetRotatedCopy(VDouble degrees)
{
    // Copy the specifications of the original.
    ImageMatrix &source = *this;
    ImageMatrix &target = CreateEmptyCopy();

    // Convert degree measurement to radians.
    double angle = degrees / 57.3;

    // ... rest of code as in attempt #3 ...

感谢所有帮助人员！

1 2 1 
0 0 0 
-1 -2 -1 

1 2 1 
0 0 0 
-1 -2 -1 

-1 0 1 
-2 0 2 
-1 0 1 

-1 -2 -1 
0 0 0 
1 2 1 

1 0 -1 
2 0 -2 
1 0 -1 

推荐答案

这是一个我破解的完整示例：
我认为你可能还没有使用弧度（我们都应该使用和爱）。我将新坐标保持在双打中，这似乎使它不那么挑剔。请注意，我没有做边界检查我应该但是我很懒。

Here is a complete example I hacked up: I think among other things you may have not been using radians (which we all should use and love). I keep the new coordinates in doubles which seemed to make it less finicky. Note that I am not doing bounds checking which I should but I was lazy.

如果你需要更快的旋转，你总是可以像这样剪切示例。

If you need a faster rotation you can always use shearing like this example.

#include <math.h>
#include <stdio.h>

#define SIZEX 3
#define SIZEY 3

int source[SIZEX][SIZEY] = {
  { 1, 0, 0 },
  { 0, 1, 0 },
  { 0, 0, 1 }
};

int target[SIZEX][SIZEY];

int main () {
  double angle = M_PI/2.0;

  memset(target,0,sizeof(int)*SIZEX*SIZEY);

  double centerX = ((double)(SIZEX-1))/2.0;
  double centerY = ((double)(SIZEY-1))/2.0;

  for (int y = 0; y < SIZEY; y++) {
    for (int x = 0; x < SIZEX; x++) {
        double dx = ((double)x)-centerX;
        double dy = ((double)y)-centerY;
        double newX = cos(angle)*dx-sin(angle)*dy+centerX;
        double newY = cos(angle)*dy+sin(angle)*dx+centerY;

        int ix = (int) round(newX);
        int iy = (int) round(newY);
        target[x][y] = source[ix][iy];
    }
  }

  for (int i=0;i<SIZEY;i++) {
    for (int j=0;j<SIZEX;j++) {
      printf("%d ", target[j][i]);
    }
    printf("\n");
  } 
}

这篇关于为什么我的图像旋转算法不起作用？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！