Gamma图像增强处理

Halcom

Gamma图像增强处理：
将设定的亮度区间拉伸或缩小处理；
I = imread('pout.tif');
J = imadjust_ysw(I);

1. function out = imadjust_ysw(img)
   
2. %IMADJUST Adjust image intensity values or colormap.
   
3. %   J = IMADJUST(I,[LOW_IN; HIGH_IN],[LOW_OUT; HIGH_OUT],GAMMA) maps the
   
4. %   values of I to new values in J as described in the previous syntax.
   
5. %   GAMMA specifies the shape of the curve describing the relationship
   
6. %   between the values in I and J. If GAMMA is less than 1, the mapping is
   
7. %   weighted toward higher (brighter) output values. If GAMMA is greater
   
8. %   than 1, the mapping is weighted toward lower (darker) output values. If
   
9. %   you omit the argument, GAMMA defaults to 1 (linear mapping).
   
10. 
    
11. %   LOW_IN, HIGH_IN, LOW_OUT, HIGH_OUT all must be in the range [0,1];
    
12. %   GAMMA         real, double, nonnegative
    
13. 
    
14. if nargin == 1
    
15.     imageType = 'intensity';
    
16.     lowIn = 0.3059;
    
17.     highIn = 0.6314;
    
18.     lowOut = 0;
    
19.     highOut = 1;
    
20.     gamma = 1;
    
21. end
    
22. 
    
23. if ~isfloat(img) && numel(img) > 65536
    
24.     % integer data type image with more than 65536 elements
    
25.     out = adjustWithLUT(img,lowIn,highIn,lowOut,highOut,gamma);
    
26. else
    
27.     classin = class(img);
    
28.     classChanged = false;
    
29.     if ~isa(img,'double')
    
30.         classChanged = true;
    
31.         img = im2double(img);
    
32.     end
    
33. 
    
34.     if strcmp(imageType, 'intensity')
    
35.         out = adjustGrayscaleImage(img,lowIn,highIn,lowOut,highOut,gamma);
    
36.     elseif strcmp(imageType, 'indexed')
    
37.         out = adjustColormap(img,lowIn,highIn,lowOut,highOut,gamma);
    
38.     else
    
39.         out = adjustTruecolorImage(img,lowIn,highIn,lowOut,highOut,gamma);
    
40.     end
    
41.    
    
42.     if classChanged
    
43.         out = images.internal.changeClass(classin,out);
    
44.     end
    
45. 
    
46. end
    
47. 
    
48. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    
49. function out = adjustWithLUT(img,lowIn,highIn,lowOut,highOut,gamma)
    
50. 
    
51. imgClass = class(img);
    
52. out = zeros(size(img),imgClass);
    
53. 
    
54. %initialize for lut
    
55. 
    
56. switch imgClass
    
57.     case 'uint8'
    
58.         lutLength = 256;
    
59.         conversionFcn = @im2uint8;
    
60.     case 'uint16'
    
61.         lutLength = 65536;
    
62.         conversionFcn = @im2uint16;
    
63.     case 'int16'
    
64.         lutLength = 65536;
    
65.         conversionFcn = @im2int16;
    
66.     otherwise
    
67.         error(message('images:imadjust:internalError'))
    
68. end
    
69. 
    
70. for p = 1:size(img,3)
    
71.     lut = linspace(0,1,lutLength);
    
72.     scalingFactor = 1;
    
73.     lut = adjustArray(lut,lowIn(p),highIn(p),lowOut(p),highOut(p), ...
    
74.         gamma(p),scalingFactor);
    
75.     lut = conversionFcn(lut);
    
76.     out(:,:,p) = intlut(img(:,:,p),lut);
    
77. end
    
78. 
    
79. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    
80. function out = adjustColormap(cmap,lIn,hIn,lOut,hOut,g)
    
81. 
    
82. % expansion factor that can expand a 1-by-3 range to the size of cmap.
    
83. expansionFactor = ones(size(cmap,1), 1);
    
84. out = adjustArray(cmap, lIn, hIn, lOut, hOut, g, expansionFactor);
    
85. 
    
86. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    
87. function out = adjustGrayscaleImage(img,lIn,hIn,lOut,hOut,g)
    
88. 
    
89. expansionFactor = 1;
    
90. out = adjustArray(img, lIn, hIn, lOut, hOut, g, expansionFactor);
    
91. 
    
92. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    
93. function out = adjustTruecolorImage(rgb,lIn,hIn,lOut,hOut,g)
    
94. 
    
95. out = zeros(size(rgb), 'like', rgb);
    
96. expansionFactor = 1;
    
97. for p = 1 : 3
    
98.     out(:,:,p) = adjustArray(rgb(:,:,p), lIn(p),hIn(p), lOut(p), ...
    
99.         hOut(p), g(p), expansionFactor);
    
100. end
     
101. 
     
102. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
     
103. function out = adjustArray(img,lIn,hIn,lOut,hOut,g,d)
     
104. 
     
105. %make sure img is in the range [lIn;hIn]
     
106. img(:) =  max(lIn(d,:), min(hIn(d,:),img));
     
107. 
     
108. out = ( (img - lIn(d,:)) ./ (hIn(d,:) - lIn(d,:)) ) .^ (g(d,:));
     
109. out(:) = out .* (hOut(d,:) - lOut(d,:)) + lOut(d,:);

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参考：【1】http://pan.baidu.com/s/1dF0B4Tr