opencv 数字图像处理-图像错切

图像的错切变换实际上是平面景物在投影平面上的非垂直投影效果。图像错切变换也称为图像剪切、错位或错移变换。图像错切的原理就是保持图像上各点的某一坐标不变，将另一个坐标进行线性变换，坐标不变的轴称为依赖轴，坐标变换的轴称为方向轴。图像错切一般分为两种情况：水平方向错切和垂直方向错切。

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水平方向的错切，即沿x轴方向关于y的错切，即x=x0+c*y0, y=y0

若c>0，则沿+x轴方向错切，反之，如果c<0，则沿-x轴方向错切.

void imageTwist(IplImage *src, IplImage *res, float ratio)
{
cvZero(res);
int res_wid;
int res_hei;

unsigned char* src_data = (unsigned char*)src->imageData;
unsigned char* res_data = (unsigned char*)res->imageData;

for (int i=0; i<src->height; i++)
{
if (ratio >= 0)
for (int j=0; j<src->width; j++)
{
res_hei=i;
res_wid=j+res_hei*ratio;
res_data[res_hei*res->widthStep+res_wid] = src_data[i*src->widthStep+j];
}
else
{
int offset=ratio*src->height;
for (int j=src->width-1; j>=0; j--)
{
res_hei=i;
res_wid=j+res_hei*ratio;
res_data[res_hei*res->widthStep+res_wid+offset] = src_data[i*src->widthStep+j];
}
}
}

cvNamedWindow("src");
cvNamedWindow("res");
cvShowImage("src", src);
cvShowImage("res", res);
cvWaitKey(0);
cvReleaseImage(&src);
cvReleaseImage(&res);
cvDestroyAllWindows();
}

void imageCutting(void)
{
src=cvLoadImage("lena.jpg", 0);
if (src == NULL)
exit(0);

float ratio;
cout<<"输入水平错切比率："<<endl;
cin>>ratio;

int res_wid;
int res_hei;
if (ratio < 0)
{
res_wid=src->width+src->height*ratio*(-1);
} else {
res_wid=src->width+src->height*ratio;
}

res_hei=src->height;
CvSize size=cvSize(res_wid, res_hei);
res=cvCreateImage(size, src->depth, src->nChannels);
if (res == NULL)
exit(0);

imageTwist(src, res, ratio);//图像扭曲
}

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垂直方向错切，即沿y轴方向关于x的错切。与水平错切类似变换，即x=x0, y=y0+b*x0

void imageTwistV(IplImage *src, IplImage *res, float ratio)
{
cvZero(res);
int res_wid;
int res_hei;

unsigned char* src_data = (unsigned char*)src->imageData;
unsigned char* res_data = (unsigned char*)res->imageData;

for (int i=0; i<src->width; i++)
{
if (ratio >= 0)
{
int offset=ratio*src->width;
for (int j=0; j<src->height; j++)
{
res_wid=i;
res_hei=j+offset-res_wid*ratio;
res_data[res_hei*res->widthStep+res_wid] = src_data[j*src->widthStep+i];
}
}
else
{
//int offset=ratio*src->height*(-1);
for (int j=src->height-1; j>=0; j--)
{
res_wid=i;
res_hei=j+res_wid*ratio*(-1);
res_data[res_hei*res->widthStep+res_wid] = src_data[j*src->widthStep+i];
}
}
}

cvNamedWindow("src");
cvNamedWindow("res");
cvShowImage("src", src);
cvShowImage("res", res);
cvWaitKey(0);
cvReleaseImage(&src);
cvReleaseImage(&res);
cvDestroyAllWindows();
}

void imageCutting(void)
{
src=cvLoadImage("lena.jpg", 0);
if (src == NULL)
exit(0);

float ratio=0;
cout<<"输入垂直错切比率："<<endl;
cin>>ratio;

int res_wid;
int res_hei;
if (ratio < 0)
{
res_hei=src->height+src->width*ratio*(-1);
//res_wid=src->width+src->height*ratio*(-1);
} else {
res_hei=src->height+src->width*ratio;
//res_wid=src->width+src->height*ratio;
}

res_wid=src->width;
//res_hei=src->height;
CvSize size=cvSize(res_wid, res_hei);
res=cvCreateImage(size, src->depth, src->nChannels);
if (res == NULL)
exit(0);

//	imageTwistH(src, res, ratio);//图像扭曲
imageTwistV(src, res, ratio);
}