数字图像管理方案计划解决方法实验报告(三四五).doc
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1、实验三 图像的几何变换一实验目的及要求掌握图像几何变换的基本原理,熟练掌握数字图像的缩放、旋转、平移、镜像和转置的基本原理及其MATLAB编程实现方法。二、实验内容(一)研究以下程序,分析程序功能;输入执行各命令行,认真观察命令执行的结果。熟悉程序中所使用函数的调用方法,改变有关参数,观察试验结果。1. 图像缩放clear all, close allI = imread(cameraman.tif);Scale = 1.35; % 将图像放大1.35倍J1 = imresize(I, Scale, nearest); % using the nearest neighbor interpol
2、ationJ2 = imresize(I, Scale, bilinear); % using the bilinear interpolationimshow(I), title(Original Image);figure, imshow(J1), title(Resized Image- using the nearest neighbor interpolation );figure, imshow(J2), title(Resized Image- using the bilinear interpolation );% 查看imresize使用帮助help imresizeComm
3、and窗口显示如下:IMRESIZE Resize image. B = IMRESIZE(A, SCALE) returns an image that is SCALE times the size of A, which is a grayscale, RGB, or binary image. B = IMRESIZE(A, NUMROWS NUMCOLS) resizes the image so that it has the specified number of rows and columns. Either NUMROWS or NUMCOLS may be NaN, in
4、 which case IMRESIZE computes the number of rows or columns automatically in order to preserve the image aspect ratio. Y, NEWMAP = IMRESIZE(X, MAP, SCALE) resizes an indexed image. Y, NEWMAP = IMRESIZE(X, MAP, NUMROWS NUMCOLS) resizes an indexed image. To control the interpolation method used by IMR
5、ESIZE, add a METHOD argument to any of the syntaxes above, like this: IMRESIZE(A, SCALE, METHOD) IMRESIZE(A, NUMROWS NUMCOLS, METHOD), IMRESIZE(X, MAP, M, METHOD) IMRESIZE(X, MAP, NUMROWS NUMCOLS, METHOD) METHOD can be a string naming a general interpolation method: nearest - nearest-neighbor interp
6、olation bilinear - bilinear interpolation bicubic - cubic interpolation; the default method METHOD can also be a string naming an interpolation kernel: box - interpolation with a box-shaped kernel triangle - interpolation with a triangular kernel (equivalent to bilinear) cubic - interpolation with a
7、 cubic kernel (equivalent to bicubic) lanczos2 - interpolation with a Lanczos-2 kernel lanczos3 - interpolation with a Lanczos-3 kernel Finally, METHOD can be a two-element cell array of the form f,w, where f is the function handle for a custom interpolation kernel, and w is the custom kernels width
8、. f(x) must be zero outside the interval -w/2 = x w/2. Your function handle f may be called with a scalar or a vector input. You can achieve additional control over IMRESIZE by using parameter/value pairs following any of the syntaxes above. For example: B = IMRESIZE(A, SCALE, PARAM1, VALUE1, PARAM2
9、, VALUE2, .) Parameters include: Antialiasing - true or false; specifies whether to perform antialiasing when shrinking an image. The default value depends on the interpolation method you choose. For the nearest method, the default is false; for all other methods, the default is true. Colormap - (on
10、ly relevant for indexed images) original or optimized; if original, then the output newmap is the same as the input map. If it is optimized, then a new optimized colormap is created. The default value is optimized. Dither - (only for indexed images) true or false; specifies whether to perform color
11、dithering. The default value is true. Method - As described above OutputSize - A two-element vector, MROWS NCOLS, specifying the output size. One element may be NaN, in which case the other value is computed automatically to preserve the aspect ratio of the image. Scale - A scalar or two-element vec
12、tor specifying the resize scale factors. If it is a scalar, the same scale factor is applied to each dimension. If it is a vector, it contains the scale factors for the row and column dimensions, respectively. Examples - Shrink by factor of two using the defaults of bicubic interpolation and antiali
13、asing. I = imread(rice.png); J = imresize(I, 0.5); figure, imshow(I), figure, imshow(J) Shrink by factor of two using nearest-neighbor interpolation. (This is the fastest method, but it has the lowest quality.) J2 = imresize(I, 0.5, nearest); Resize an indexed image. X, map = imread(trees.tif); Y, n
14、ewmap = imresize(X, map, 0.5); imshow(Y, newmap) Resize an RGB image to have 64 rows. The number of columns is computed automatically. RGB = imread(peppers.png); RGB2 = imresize(RGB, 64 NaN); Note - The function IMRESIZE in previous versions of the Image Processing Toolbox used a somewhat different
15、algorithm by default. If you need the same results produced by the previous implementation, call the function IMRESIZE_OLD. Class Support - The input image A can be numeric or logical and it must be nonsparse. The output image is of the same class as the input image. The input indexed image X can be
16、 uint8, uint16, or double. See also imresize_old, imrotate, imtransform, tformarray. Reference page in Help browser doc imresize执行程序所得结果如下:改变参数Scale =0.5得到图形结果如下:对以上实验结果,分析如下:通过查看命令窗口查看imresize函数的使用方法。本实验中利用了形式B = imresize(A,m,method)。实验中method采用了,nearest(默认值)最近邻插值 方法和bilinear双线性插值方法,由图片显示结果可以看出,双线性
17、插值方法要好于最近邻插值方法。这是由于最近邻插值方法仅是取离其最近的一个像素的像素值,而双线性插值方法采用了其周围的像素值参与计算,所以更能适应图像的局部特征。m为放大倍数,由上面实验结果可以明显看出,放大1.35倍和0.5倍的效果差异。2. 图像旋转clear all, close allI = imread(cameraman.tif);Theta = 45; % 将图像逆时针旋转45。J1 = imrotate(I, Theta, nearest); % using the nearest neighbor interpolation%and enlarge the output ima
18、geTheta = -45; % 将图像顺时针旋转45。J2 = imrotate(I, Theta, bilinear, crop); % using the bilinear interpolation % and crops the output image imshow(I), title(Original Image);figure, imshow(J1), title(Rotated Image- using the nearest neighbor interpolation );figure, imshow(J2), title( Rotated Image- using th
19、e bilinear interpolation );% 查看imrotate使用帮助help imrotateCommand窗口显示如下:IMROTATE Rotate image. B = IMROTATE(A,ANGLE) rotates image A by ANGLE degrees in a counterclockwise direction around its center point. To rotate the image clockwise, specify a negative value for ANGLE. IMROTATE makes the output im
20、age B large enough to contain the entire rotated image. IMROTATE uses nearest neighbor interpolation, setting the values of pixels in B that are outside the rotated image to 0 (zero). B = IMROTATE(A,ANGLE,METHOD) rotates image A, using the interpolation method specified by METHOD. METHOD is a string
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