c - C 中的旋转算法？

Question

我想在图像上应用角度 alpha 的旋转，但我的函数没有给我预期的结果。我必须将它用于 OCR 项目。

我使用了以下结构:

struct pixel
{
  int red;
  int blue;
  int green;
  int alpha;
};

struct image_bw
{
  int *img;
  int w;
  int h;
};

struct image_rgb
{
  int h;
  int w;
  struct pixel* img;
};

这是我的功能:

void rotation_tab(int alpha,struct image_bw* img)
{


 int w = img->w;
 int h = img->h;

 float radians = (2*3.1416*alpha)/360;

 float cosine = (float)cos(-radians);
 float sine = (float)sin(-radians);

 float Point1x=(h*sine);
 float Point1y=(h*cosine);
 float Point2x=(w*cosine-h*sine);
 float Point2y=(h*cosine+w*sine);
 float Point3x=(w*cosine);
 float Point3y=(w*sine);

 float minx=fmin(0,fmin(Point1x,fmin(Point2x,Point3x)));
 float miny=fmin(0,fmin(Point1y,fmin(Point2y,Point3y)));
 float maxx=fmax(0,fmax(Point1x,fmax(Point2x,Point3x)));
 float maxy=fmax(0,fmax(Point1y,fmax(Point2y,Point3y)));

 int destX = (int)ceil(fabs(maxx-minx));
 int destY = (int)ceil(fabs(maxy-miny));
 int *tab = malloc((sizeof(int))*destX*destY);

 int midx = w/2;
 int midy = h/2;

 for (int x = 0; x < w; x++)
 {
   for (int y = 0; y < h; y++)
   {
     int xt = x - midx;
     int yt = y - midy;

     int xs = (int)round((cosine*xt - sine*yt) + midx);
     int ys = (int)round((sine*xt + cosine*yt) + midy);
     if ((xs >= 0) && (xs<w) && (ys>=0) && (ys<h))
     {
       tab[xs+ys*destX] = (img->img)[x+y*w];
     }
   }
 }
 img->w = destX;
 img->h = destY;
 img->img = tab;
}

Answer 1

如果你在任何有精细细节的东西上使用它，就会产生楼梯、莫尔图案和其他 block 状图案。您想使用插值来混合最接近计算坐标的像素。而不仅仅是四舍五入。