OpenCV图像缩放resize函数

布满荆棘的人生 2023-02-12 06:22 66阅读 0赞

## API ##

*  c++

void cv::resize	(	InputArray 	src,
    OutputArray 	dst,
    Size 	dsize,
    double 	fx = 0,
    double 	fy = 0,
    int 	interpolation = INTER_LINEAR 
    )

函数resize将图像src的大小调整到指定的大小或调整到指定的大小。注意，没有考虑初始dst类型或大小。相反，大小和类型派生自src、dsize、fx和fy。如果你想调整src的大小

// 显式地指定dsize = dst.size ();fx和fy将从这里计算
    resize(src, dst, dst.size(), 0, 0, interpolation);

如果你想要在每个方向上把图像抽取2倍，你可以这样调用函数:

// 指定fx和fy并让函数计算目标图像的大小。
    resize(src, dst, Size(), 0.5, 0.5, interpolation);

要缩小一个图像，通常使用INTER\_AREA插值效果最好，而要放大一个图像，通常使用c::INTER\_CUBIC(慢)或INTER\_LINEAR(更快，但看起来还可以)效果最好。

*  参数解释  
    ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NleHlsdW5h_size_16_color_FFFFFF_t_70]
 *  python

Python:
    dst	=	cv.resize(	src, dsize[, dst[, fx[, fy[, interpolation]]]]	)

## python示例代码 ##

> 可以通过dsize = (x,y)手动设置缩放的尺度。(samll2就是这么缩放的)

import  cv2 as cv
    
    file_name = "./data/src/1 (69).jpg"
    img = cv.imread(file_name)
    img_illumination = cv.GaussianBlur(img, (15, 15), 0)
    get_img_reflect = (img + 0.001) / (img_illumination + 0.001)
    dsize =[200,200]
    # 横纵缩放
    small = cv.resize(get_img_reflect, (0, 0), fx=0.5, fy=0.5,interpolation=cv.INTER_NEAREST)
    # 固定尺寸缩小
    small2 = cv.resize(get_img_reflect, (300, 400))
    # 原尺寸缩放
    # 获得图像的宽高
    x, y = img.shape[0:2]
    small3 = cv.resize(get_img_reflect, (int(x/2), int(y/2)))
    print(x,y)
    
    cv.imshow("50%", small3)
    
    cv.waitKey(0)

*  `small`缩放效果  
    ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NleHlsdW5h_size_16_color_FFFFFF_t_70 1]
 *  `small2`缩放效果  
    ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NleHlsdW5h_size_16_color_FFFFFF_t_70 2]
 *  `small3`参数缩放效果  
    ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NleHlsdW5h_size_16_color_FFFFFF_t_70 3]

## python的resize函数参数分析 ##

def resize(src, dsize, dst=None, fx=None, fy=None, interpolation=None): # real signature unknown; restored from __doc__
        """ resize(src, dsize[, dst[, fx[, fy[, interpolation]]]]) -> dst . @brief Resizes an image. . . The function resize resizes the image src down to or up to the specified size. Note that the . initial dst type or size are not taken into account. Instead, the size and type are derived from . the `src`,`dsize`,`fx`, and `fy`. If you want to resize src so that it fits the pre-created dst, . you may call the function as follows: . @code . // explicitly specify dsize=dst.size(); fx and fy will be computed from that. . resize(src, dst, dst.size(), 0, 0, interpolation); . @endcode . If you want to decimate the image by factor of 2 in each direction, you can call the function this . way: . @code . // specify fx and fy and let the function compute the destination image size. . resize(src, dst, Size(), 0.5, 0.5, interpolation); . @endcode . To shrink an image, it will generally look best with #INTER_AREA interpolation, whereas to . enlarge an image, it will generally look best with c#INTER_CUBIC (slow) or #INTER_LINEAR . (faster but still looks OK). . . @param src input image. . @param dst output image; it has the size dsize (when it is non-zero) or the size computed from . src.size(), fx, and fy; the type of dst is the same as of src. . @param dsize output image size; if it equals zero, it is computed as: . \f[\texttt{dsize = Size(round(fx*src.cols), round(fy*src.rows))}\f] . Either dsize or both fx and fy must be non-zero. . @param fx scale factor along the horizontal axis; when it equals 0, it is computed as . \f[\texttt{(double)dsize.width/src.cols}\f] . @param fy scale factor along the vertical axis; when it equals 0, it is computed as . \f[\texttt{(double)dsize.height/src.rows}\f] . @param interpolation interpolation method, see #InterpolationFlags . . @sa warpAffine, warpPerspective, remap """
        pass

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