彩色图像处理MATLAB函数简介

4 颜色空间转换函数的编写


function hsi=rgb2hsi(rgb) %将RGB图像转换成HSI图像 rgb=im2double(rgb); r=rgb(:,:,1); g=rgb(:,:,2); b=rgb(:,:,3);
4 颜色空间转换函数的编写



4 颜色空间转换函数的编写


%GB区间（120-240） idx=find((2*pi/3<=H)&(H<4*pi/3)); R(idx)=I(idx).*(1-S(idx)); G(idx)=I(idx).*(1+S(idx).*cos(H(idx)2*pi/3)./cos(pi-H(idx))); B(idx)=3*I(idx)-(R(idx)+G(idx));
%将RGB转换HSI num=0.5*((r-g)+(r-b)); den=sqrt((r-g).^2+(r-b).*(g-b)); theta=acos(num./(den+eps)); H=theta; h(b>g)=2*pi-H(b>g); H=H/(2*pi); num=min(min(r,g),b); den=r+g+b; den(den==0)=eps; S=1-3.*num./den; I=(r+g+b)/3; hsi=cat(3,H,S,I);
figure(2) imshow(fr) title('red component') figure(3) imshow(fg) title('green component') figure(4) imshow(fb) title('blue component')
编程应用

4 颜色空间转换函数的编写

function rgb=hsi2rgb(hsi) %将HSI图像转换成RGB图像 H=hsi(:,:,1)*2*pi; S=hsi(:,:,2); I=hsi(:,:,3); %初始化 R=zeros(size(hsi,1),size(hsi,2)); G=zeros(size(hsi,1),size(hsi,2)); B=zeros(size(hsi,1),size(hsi,2));
1 函数简介

ind2gray ind2rgb
mat2gray rgb2gray rgb2ind
- Convert indexed image to intensity image. - Convert indexed image to RGB image (MATLAB Toolbox). - Convert matrix to intensity image. - Convert RGB image or colormap to grayscale. - Convert RGB image to indexed image.
编程应用



%仅对HSV图像的v分量滤波 v_filtered=imfilter(v,w,'replicate'); h=cat(3,h,s,v_filtered); f_filtered=hsv2rgb(h); f_filtered=min(f_filtered,1); figure(10) imshow(f_filtered) title('filtered hsv image')
3 颜色空间转换函数举例

hsv2rgb Convert HSV colormap to RGB colormap M = hsv2rgb(H) Description converts a hue-saturation-value (HSV) colormap to a red-green-blue (RGB) colormap. H is an m-by-3 matrix, where m is the number of colors in the colormap. The columns of H represent hue, saturation, and value, respectively. M is an m-by-3 matrix. Its columns are intensities of red, green, and blue, respectively.
编程应用



fc=imread('peppers.png'); %提取RGB分量 fr=fc(:,:,1); fg=fc(:,:,2); fb=fc(:,:,3); figure(1) imshow(f) title('rgb image')
编程应用

1 函数简介

rgb2hsv
rgb2ntsc rgb2ycbcr
whitepoint xyz2double xyz2uint16 ycbcr2rgb


- Convert RGB values to HSV color space (MATLAB Toolbox). - Convert RGB values to NTSC color space. - Convert RGB values to YCBCR color space. - Returns XYZ values of standard illuminants. - Convert XYZ color values to double. - Convert XYZ color values to uint16. - Convert YCBCR values to RGB color space.
%将RGB转换成HSV hc=rgb2hsv(fc); %提取HSV分量 h=hc(:,:,1); s=hc(:,:,2); v=hc(:,:,3); figure(5) imshow(hsv2rgb(hc)) title('hsv image')
编程应用


ห้องสมุดไป่ตู้
%显示HSV分量图像 figure(6) imshow(h) title('hue component') figure(7) imshow(s) title('saturation component') figure(8) imshow(v) title('value component')
编程应用



%产生均值滤波器 w=fspecial('average',5); %对RGB图像滤波 rgb_filtered=imfilter(fc,w,'replicate'); figure(9) imshow(rgb_filtered) title('filtered RGB image')

‘type’ 参数
‘type’ 参数
颜色空间
应用

rgb = imread('peppers.png'); cform = makecform('srgb2lab'); lab = applycform(rgb,cform);
3 颜色空间转换函数举例

rgb2hsv Convert RGB colormap to HSV colormap cmap = rgb2hsv(M) Description converts an RGB colormap M to an HSV colormap cmap. Both colormaps are m-by-3 matrices. The elements of both colormaps are in the range 0 to 1. The columns of the input matrix M represent intensities of red, green, and blue, respectively. The columns of the output matrix cmap represent hue, saturation, and value, respectively.
彩色图像处理函数简介
1 函数简介

applycform


- Apply device-independent color space transformation. hsv2rgb - Convert HSV values to RGB color space (MATLAB Toolbox). iccread - Read ICC color profile. lab2double - Convert Lab color values to double. lab2uint16 - Convert Lab color values to uint16. lab2uint8 - Convert Lab color values to uint8. makecform - Create device-independent color space transform structure. ntsc2rgb - Convert NTSC values to RGB color space.
2 颜色空间转换矩阵的创建与应用
makecform Create a color transformation structure Syntax C = makecform(type) creates the color transformation structure C that defines the color space conversion specified by type. To perform the transformation, pass the color transformation structure as an argument to the applycform function.
编程应用

%对h,s,v同时滤波 h_filtered=imfilter(h,w,'replicate'); s_filtered=imfilter(s,w,'replicate'); v_filtered=imfilter(v,w,'replicate'); h=cat(3,h_filtered,s_filtered,v_filtered); f_filtered=hsv2rgb(h); f_filtered=min(f_filtered,1); figure(11) imshow(f_filtered)
4 颜色空间转换函数的编写


%分区转换 %RB区间（0-120） idx=find((0<=H)&(H<2*pi/3)); B(idx)=I(idx).*(1-S(idx)); R(idx)=I(idx).*(1+S(idx).*cos(H(idx))./ cos(pi/3-H(idx))); G(idx)=3*I(idx)-(R(idx)+B(idx));
1 函数简介



dither gray2ind grayslice
- Convert image using dithering. - Convert intensity image to indexed image. - Create indexed image from intensity image by thresholding. graythresh - Compute global image threshold using Otsu's method. im2bw - Convert image to binary image by thresholding. im2double - Convert image array to double precision.