/*
Converts an image to 8-bit grayscale and Gaussian-smooths it. The image is
optionally doubled in size prior to smoothing.
@param img input image
@param img_dbl if true, image is doubled in size prior to smoothing
@param sigma total std of Gaussian smoothing
*/
static IplImage* create_init_img( IplImage* img, int img_dbl, double sigma )
{
IplImage* gray, * dbl;
double sig_diff;
gray = convert_to_gray32( img );
if( img_dbl )
{
sig_diff = sqrt( sigma * sigma - SIFT_INIT_SIGMA * SIFT_INIT_SIGMA * 4 );
dbl = cvCreateImage( cvSize( img->width*2, img->height*2 ),
IPL_DEPTH_32F, 1 );
cvResize( gray, dbl, CV_INTER_CUBIC );
cvSmooth( dbl, dbl, CV_GAUSSIAN, 0, 0, sig_diff, sig_diff );
cvReleaseImage( &gray );
return dbl;
}
else
{
sig_diff = sqrt( sigma * sigma - SIFT_INIT_SIGMA * SIFT_INIT_SIGMA );
cvSmooth( gray, gray, CV_GAUSSIAN, 0, 0, sig_diff, sig_diff );
//start add
cvReleaseImage(&dbl);
//end add
return gray;
}
}
/*
Converts an image to 8-bit grayscale and Gaussian-smooths it. The image is
optionally doubled in size prior to smoothing.
@param img input image
@param img_dbl if true, image is doubled in size prior to smoothing
@param sigma total std of Gaussian smoothing
*/
static IplImage* create_init_img( IplImage* img, int img_dbl, double sigma )
{
IplImage* gray, * dbl;
float sig_diff;
gray = convert_to_gray32( img );
if( img_dbl )
{
sig_diff = sqrt( sigma * sigma - SIFT_INIT_SIGMA * SIFT_INIT_SIGMA * 4 );
dbl = cvCreateImage( cvSize( img->width*2, img->height*2 ),
IPL_DEPTH_32F, 1 );
cvResize( gray, dbl, CV_INTER_CUBIC );
cvSmooth( dbl, dbl, CV_GAUSSIAN, 0, 0, sig_diff, sig_diff );
cvReleaseImage( &gray );
return dbl;
}
else
{
//assume that the original image has a blur of at least 0.5,and that therefore
//the doubled image has sig=1
sig_diff = sqrt( sigma * sigma - SIFT_INIT_SIGMA * SIFT_INIT_SIGMA );
cvSmooth( gray, gray, CV_GAUSSIAN, 0, 0, sig_diff, sig_diff );
return gray;
}
}
/*
Converts an image to 32-bit grayscale and Gaussian-smooths it. The image is
optionally doubled in size prior to smoothing.
@param img input image
@param img_dbl if true, image is doubled in size prior to smoothing
@param sigma total std of Gaussian smoothing
*/
static IplImage* create_init_img( IplImage* img, int img_dbl, double sigma )
{
IplImage* gray, * dbl;
float sig_diff;
//调用函数，将输入图像转换为32位灰度图，并归一化
gray = convert_to_gray32( img );
//若设置了将图像放大为原图的2倍
if( img_dbl )
{
//将图像长宽扩展一倍时，便有了底-1层，该层尺度为：
sig_diff = sqrt( sigma * sigma - SIFT_INIT_SIGMA * SIFT_INIT_SIGMA * 4 );
dbl = cvCreateImage( cvSize( img->width*2, img->height*2 ),IPL_DEPTH_32F, 1 );//创建放大图像
cvResize( gray, dbl, CV_INTER_CUBIC );//放大原图的尺寸
//高斯平滑，高斯核在x,y方向上的标准差都是sig_diff
cvSmooth( dbl, dbl, CV_GAUSSIAN, 0, 0, sig_diff, sig_diff );
cvReleaseImage( &gray );
return dbl;
}
else//不用放大为原图的2倍
{
//计算第0层的尺度
sig_diff = sqrt( sigma * sigma - SIFT_INIT_SIGMA * SIFT_INIT_SIGMA );
//高斯平滑，高斯核在x,y方向上的标准差都是sig_diff
cvSmooth( gray, gray, CV_GAUSSIAN, 0, 0, sig_diff, sig_diff );
return gray;
}
}
