CV_EXPORTS_W Mat imread( const String& filename, int flags = IMREAD_COLOR );
enum ImreadModes {
IMREAD_UNCHANGED = -1,
//!< If set, return the loaded image as is (with alpha channel, otherwise it gets cropped). Ignore EXIF orientation.
IMREAD_GRAYSCALE = 0,
//!< If set, always convert image to the single channel grayscale image (codec internal conversion).
IMREAD_COLOR = 1,
//!< If set, always convert image to the 3 channel BGR color image.
IMREAD_ANYDEPTH = 2,
//!< If set, return 16-bit/32-bit image when the input has the corresponding depth, otherwise convert it to 8-bit.
IMREAD_ANYCOLOR = 4,
//!< If set, the image is read in any possible color format.
IMREAD_LOAD_GDAL = 8,
//!< If set, use the gdal driver for loading the image.
IMREAD_REDUCED_GRAYSCALE_2 = 16,
//!< If set, always convert image to the single channel grayscale image and the image size reduced 1/2.
IMREAD_REDUCED_COLOR_2 = 17,
//!< If set, always convert image to the 3 channel BGR color image and the image size reduced 1/2.
IMREAD_REDUCED_GRAYSCALE_4 = 32,
//!< If set, always convert image to the single channel grayscale image and the image size reduced 1/4.
IMREAD_REDUCED_COLOR_4 = 33,
//!< If set, always convert image to the 3 channel BGR color image and the image size reduced 1/4.
IMREAD_REDUCED_GRAYSCALE_8 = 64,
//!< If set, always convert image to the single channel grayscale image and the image size reduced 1/8.
IMREAD_REDUCED_COLOR_8 = 65,
//!< If set, always convert image to the 3 channel BGR color image and the image size reduced 1/8.
IMREAD_IGNORE_ORIENTATION = 128
//!< If set, do not rotate the image according to EXIF's orientation flag.
};
2.创建窗口
CV_EXPORTS_W void namedWindow(const String& winname, int flags = WINDOW_AUTOSIZE);
enum InterpolationFlags{
/** nearest neighbor interpolation */
INTER_NEAREST = 0,
/** bilinear interpolation */
INTER_LINEAR = 1,
/** bicubic interpolation */
INTER_CUBIC = 2,
/** resampling using pixel area relation. It may be a preferred method for image decimation, as
it gives moire'-free results. But when the image is zoomed, it is similar to the INTER_NEAREST
method. */
INTER_AREA = 3,
/** Lanczos interpolation over 8x8 neighborhood */
INTER_LANCZOS4 = 4,
/** Bit exact bilinear interpolation */
INTER_LINEAR_EXACT = 5,
/** Bit exact nearest neighbor interpolation. This will produce same results as
the nearest neighbor method in PIL, scikit-image or Matlab. */
INTER_NEAREST_EXACT = 6,
/** mask for interpolation codes */
INTER_MAX = 7,
/** flag, fills all of the destination image pixels. If some of them correspond to outliers in the
source image, they are set to zero */
WARP_FILL_OUTLIERS = 8,
/** flag, inverse transformation
For example, #linearPolar or #logPolar transforms:
- flag is __not__ set: \f$dst( \rho , \phi ) = src(x,y)\f$
- flag is set: \f$dst(x,y) = src( \rho , \phi )\f$
*/
WARP_INVERSE_MAP = 16
};
Mat xuenai = imread("xuenai.jpg");
imshow("xuenai", xuenai);
Mat xuenai_rotate(xuenai.size(), xuenai.type());
rotate(xuenai, xuenai_rotate, ROTATE_180);
imshow("xuenai_rotate", xuenai_rotate);
waitKet();
15.仿射变换
15.1 API
CV_EXPORTS_W void warpAffine( InputArray src, OutputArray dst,
InputArray M, Size dsize,
int flags = INTER_LINEAR,
int borderMode = BORDER_CONSTANT,
const Scalar& borderValue = Scalar());
参数如下
参数
含义
src(source)
输入图片
dst(destination)
输出图片
M
变换矩阵
dsize(destination size)
输出图片的尺寸，若不对输出图片的尺寸进行调整，那么很可能会出现黑边
flags
插值算法
borderMode
边界外推法
borderValue
填充边界的值
15.2 平移
只需将变换矩阵M设置成如下形式：
float delta_x=200,delta_y=200;
float M_values[]={1,0,delta_x,
0,1,delta_y};
Mat M(Size(3,2),CV_32F,M_values);
delta_x：x方向上的偏移量
delta_y：y方向上的偏移量
M_values：必须是浮点类型的数组对象
M：必须是CV_32F，不能用逗号式分隔创建
效果
Mat xuenai = imread("xuenai.jpg");
imshow("xuenai",xuenai);
double M_values[]={1,0,200,
0,1,200};
Mat M(Size(3,2), CV_64F,M_values);
Mat xuenai_shift(xuenai.size(),xuenai.type());
warpAffine(xuenai,xuenai_shift,M,xuenai.size());
imshow("xuenai_shift",xuenai_shift);
waitKet();
15.3 任意角度旋转
获得变换矩阵M
inline
Mat getRotationMatrix2D(Point2f center, double angle, double scale)
{
return Mat(getRotationMatrix2D_(center, angle, scale), true);
}
参数如下
参数
含义
center
旋转中心点的坐标
angle
逆时针偏角
scale
生成图与原图之比
效果
Mat xuenai = imread("xuenai.jpg");
imshow("xuenai", xuenai);
Mat M= getRotationMatrix2D(Point2f(xuenai.cols/2,xuenai.rows/2),45,1);
Mat xuenai_rotate(xuenai.size(),xuenai.type());
warpAffine(xuenai,xuenai_rotate,M,xuenai.size());
imshow("xuenai_flip",xuenai_rotate);
15.4 仿射（不破坏几何关系）
获得变换矩阵M
CV_EXPORTS Mat getAffineTransform( const Point2f src[], const Point2f dst[] );
参数如下
参数
含义
src[](source[])
输入图片的坐标点集，含三个坐标点
dst[](destination[])
三个坐标点变换的目标位置
三个点要一一对应
16.透射变换（破坏几何关系）
16.1 API
进行变换
CV_EXPORTS_W void warpPerspective( InputArray src, OutputArray dst,
InputArray M, Size dsize,
int flags = INTER_LINEAR,
int borderMode = BORDER_CONSTANT,
const Scalar& borderValue = Scalar());
参数如下
参数
含义
src(source)
输入图片
dst(destination)
输出图片
M
变换矩阵
dsize(destination size)
输出图片的尺寸，若不对输出图片的尺寸进行调整，那么很可能会出现黑边
flags
插值算法
borderMode
边界外推法
borderValue
填充边界的值
已知变换后图片，逆推变换矩阵M
CV_EXPORTS_W Mat getPerspectiveTransform(InputArray src, InputArray dst, int solveMethod = DECOMP_LU);
参数如下
参数
含义
src(source)
输入图片
dst(destination)
输出图片
获得变换矩阵M
CV_EXPORTS Mat getPerspectiveTransform(const Point2f src[], const Point2f dst[], int solveMethod = DECOMP_LU);
参数如下
参数
含义
src[](source[])
输入图片的坐标点集，含四个坐标点
dst[](destination[])
三个坐标点变换的目标位置
四个点要一一对应
16.2 效果
Mat origin = imread("origin.jpg");
Point2f point2F_origin[4]={Point2f (405,105),Point2f(2469,217),Point2f(2573,3489),Point2f(349,3547)};
Point2f point2F_tansform[4]={Point2f (0,0),Point2f(2500,0),Point2f(2500,3500),Point2f(0,3500)};
Mat M=getPerspectiveTransform(point2F_origin,point2F_tansform);
Mat transfrom(origin.size(),origin.type());
warpPerspective(origin,transfrom,M,Size(2500,3500));
resize(origin,origin,Size(500,700));
resize(transfrom,transfrom,Size(500,700));
imshow("origin",origin);
imshow("transform",transfrom);
