数字图像处理（一）：灰度变换和直方图处理

1.利用对数变换减小动态范围

f = imread('E:【数字图像处理】ImagesDIP3E_Original_Images_CH03Fig0305(a)(DFT_no_log).tif');
g = im2uint8(mat2gray(log(1+double(f))));
imshow(g);

2.负片处理两种方式

g = imadjust(f,[0 1],[1 0]);%负片处理
g = imcomplement(f);%负片处理

3.突出感兴趣的灰度区

g = imadjust(f,[0.5 0.75],[0 1]);

4.改变gamma的值来增强图像

g = imadjust(f,[ ],[ ],2);

*gamma>1时调暗，gamma<1时调亮

5.对比度拉伸

g = imadjust(f,stretchlim(f),[1 0]);

6.利用intrans实现对比度拉伸

g = intrans(f,'stretch',mean2(tofloat(f)),0.9);

 7.绘制图像的直方图

p = imhist(f)/numel(f);%归一化
imhist(p)

 8.直方图均衡：扩展了图像的动态范围，提高对比度

f = imread('E:【数字图像处理】ImagesDIP3E_Original_Images_CH03Fig0310(b)(washed_out_pollen_image).tif');%读入图像
imshow(f);%显示图像
figure(2);
imhist(f);%绘制直方图
ylim('auto');%自动设置y轴上下限范围
g=histeq(f,256);%直方图均衡,256为设定的灰度级数，不设的话默认为64
figure(3)
imshow(g);
figure(4)
imhist(g);
ylim('auto');

%直方图均衡化
I = imread('E:【数字图像处理】ImagesDIP3E_Original_Images_CH03Fig0310(b)(washed_out_pollen_image).tif');
[height,width] = size(I);
figure
subplot(221)
imshow(I)%显示原始图像
subplot(222)
imhist(I)%显示原始图像直方图
ylim('auto');

%进行像素灰度统计;
NumPixel = zeros(1,256);%统计各灰度数目，共256个灰度级
for i = 1:height
    for j = 1: width
        NumPixel(I(i,j) + 1) = NumPixel(I(i,j) + 1) + 1;%对应灰度值像素点数量增加一
    end
end
%计算灰度分布密度
ProbPixel = zeros(1,256);
for i = 1:256
    ProbPixel(i) = NumPixel(i) / (height * width * 1.0);
end
%计算累计直方图分布
CumuPixel = zeros(1,256);
for i = 1:256
    if i == 1
        CumuPixel(i) = ProbPixel(i);
    else
        CumuPixel(i) = CumuPixel(i - 1) + ProbPixel(i);
    end
end
%累计分布取整
CumuPixel = uint8(255 .* CumuPixel +0.5);
%对灰度值进行映射（均衡化）
for i = 1:height
    for j = 1: width
        I(i,j) = CumuPixel(I(i,j)+1);
    end
end

subplot(223)
imshow(I)%显示均衡化后图像
subplot(224)
imhist(I)%显示均衡化后图像直方图
ylim('auto')
xlim('auto')