图像相关术语:
像素
DPI
PPI
位,颜色
色图
图像类型
二值图像
>> bw=imread('12.png');
>> figure(2)
>> imshow(~bw)
figure(1)
>> imshow(bw)
>> info=imfinfo('12.png');
>> info
info =
Filename: '12.png'
FileModDate: '13-May-2009 23:26:04'
FileSize: 9820
Format: 'png'
FormatVersion: []
Width: 971
Height: 971
BitDepth: 1
ColorType: 'grayscale'
FormatSignature: [137 80 78 71 13 10 26 10]
Colormap: []
Histogram: []
InterlaceType: 'none'
Transparency: 'none'
SimpleTransparencyData: []
BackgroundColor: []
RenderingIntent: []
Chromaticities: [1x8 double]
Gamma: 0.4545
XResolution: 15748
YResolution: 15748
ResolutionUnit: 'meter'
XOffset: []
YOffset: []
OffsetUnit: []
SignificantBits: []
ImageModTime: []
Title: []
Author: []
Description: []
Copyright: []
CreationTime: []
Software: []
Disclaimer: []
Warning: []
Source: []
Comment: []
OtherText: []
RGB图像
又称真彩图像
实例:
>> info=imfinfo('13.jpg');
>> info
info =
Filename: '13.jpg'
FileModDate: '14-May-2009 00:03:44'
FileSize: 151529
Format: 'jpg'
FormatVersion: ''
Width: 1024
Height: 724
BitDepth: 24
ColorType: 'truecolor'
FormatSignature: ''
NumberOfSamples: 3
CodingMethod: 'Huffman'
CodingProcess: 'Sequential'
Comment: {}
>> rgb=imread('13.jpg');
>> imshow(rgb);
>> rgb(12,9,:)
ans(:,:,1) =
206
ans(:,:,2) =
132
ans(:,:,3) =
9
>>
info=imfinfo('13.jpg')
将出现如下信息: 选择部分信息:
105 91 77 82 99 117 118 110 124 114 98
100 77 63 80 106 120 114 105 131 123 112
Columns 980 through 990
24 24 24 24 24 24 24 24 24 24 24
24 24 24 24 24 24 24 24 24 24 24
24 24 24 24 24 24 24 24 24 24 24
24 24 24 24 24 24 24 24 24 24 24
24 24 24 24 24 24 24 24 24 24 24
24 24 24 24 24 24 24 24 24 24 24
114 117 121 124 124 106 106 109 115 120 118
103 107 113 117 118 117 112 108 109 113 115
83 81 86 99 112 106 114 118 113 107 107
77 72 74 83 90 90 99 107 108 108 110
87 81 79 77 76 71 81 92 101 108 114
105 100 93 83 76 63 71 83 95 108 117
Columns 991 through 1001
24 24 24 24 24 24 24 24 24 24 24
24 24 24 24 24 24 24 24 24 24 24
24 24 24 24 24 24 24 24 24 24 24
24 24 24 24 24 24 24 24 24 24 24
24 24 24 24 24 24 24 24 24 24 24
24 24 24 24 24 24 24 24 24 24 24
112 107 110 124 109 85 72 55 62 98 109
110 113 110 114 117 111 98 85 77 75 80
112 112 114 114 114 113 107 98 89 82 75
114 110 118 114 112 115 118 114 103 92 76
116 110 119 114 112 117 124 122 111 99 84
Columns 1002 through 1012
24 24 24 24 24 24 24 24 24 24 24
24 24 24 24 24 24 24 24 24 24 24
24 24 24 24 24 24 24 24 24 24 24
24 24 24 24 24 24 24 24 24 24 24
116 116 117 119 114 114 115 114 109 96 79
116 116 117 119 115 114 115 114 109 95 78
116 116 117 119 116 115 116 114 109 95 77
116 116 117 119 118 116 116 114 109 94 76
Column 1024
24
24
24
24
>>i=rgh2gray(rgb) 把
>> imshow(i);
真彩图像分解:
x=imadd(rgb(:,:,1),rgb(:,:,2))
>> z=imadd(x,rgb(:,:,3));
>> imshow(z);
>> imshow(x);
实验证明:这样无法复原原来图片;
灰度图像
灰度图像是每个像素只有一个采样颜色的图像。这类图像通常显示为从最暗黑色到最亮的白色的灰度，尽管理论上这个采样可以任何颜色的不同深浅，甚至可以是不同亮度上的不同颜色。
灰度图像与黑白图像不同，在计算机图像领域中黑白图像只有黑色与白色两种颜色；灰度图像在黑色与白色之间还有许多级的颜色深度。但是，在数字图像领域之外，“黑白图像”也表示“灰度图像”，例如灰度的照片通常叫做“黑白照片”。在一些关于数字图像的文章中单色图像等同于灰度图像，在另外一些文章中又等同于黑白图像。
灰度图像经常是在单个电磁波频谱如可见光内测量每个像素的亮度得到的。
用于显示的灰度图像通常用每个采样像素 8 位的非线性尺度来保存，这样可以有 256 级灰度。这种精度刚刚能够避免可见的条带失真，并且非常易于编程。在医学图像与遥感图像这些技术应用中经常采用更多的级数以充分利用每个采样 10 或 12 位的传感器精度，并且避免计算时的近似误差。在这样的应用领域每个采样 16 位即 65536 级得到流行。
接下来的一些实验里头，将用一些例子来分析这两者的不同
>> j=imread('5.jpg');
>> subplot(121);
>> imshow(j)
>> subplot(122);
>> imshow(j,[100,200]);
>> figure ;
>> subplot(122);
>> imshow(j,20);
索引图像
http://topic.csdn.net/u/20070505/16/3399cca4-4499-4438-8a7c-b2722141ba8f.html
图像格式
ｂｍｐ
ｊｐｇ
ｐｎｇ
ｔｉｆ
ｇｉｆ
图像查询:
info=imfinfo('6.bmp')
info =
Filename: '6.bmp'
FileModDate: '13-May-2009 15:26:56'
FileSize: 786486
Format: 'bmp'
FormatVersion: [1x33 char]
Width: 512
Height: 512
BitDepth: 24
ColorType: 'truecolor'
FormatSignature: 'BM'
NumColormapEntries: 0
Colormap: []
RedMask: []
GreenMask: []
BlueMask: []
ImageDataOffset: 54
BitmapHeaderSize: 40
NumPlanes: 1
CompressionType: 'none'
BitmapSize: 786432
HorzResolution: 0
VertResolution: 0
NumColorsUsed: 0
NumImportantColors: 0
6.bmp
图像类型的转换和判断;为什么要进行转换？因为很多图像处理工作对图像类型是有特定的要求的，比如对一幅索引图像首先要将它转化为真彩图像，否则，直接滤波是没有效果的．
info=imfinfo('15.jpg')
info
info =
Filename: '15.jpg'
FileModDate: '14-May-2009 12:33:14'
FileSize: 35696
Format: 'jpg'
FormatVersion: ''
Width: 700
Height: 525
BitDepth: 24
ColorType: 'truecolor'
FormatSignature: ''
NumberOfSamples: 3
CodingMethod: 'Huffman'
CodingProcess: 'Sequential'
Comment: {}
[x,map]=imread('15.jpg');
>> Image_Type_YN1=isind(x);
Warning: isind is obsolete and may be removed in the future.
See product release notes for more information.
> In isind at 32
>> disp(Image_Type_YN1)
0
[x,map]=rgb2ind(x,0.5);
>> Image_Type_YN2=isind(x);
Warning: isind is obsolete and may be removed in the future.
See product release notes for more information.
> In isind at 32
>> Image_Type_YN2
Image_Type_YN2 =
1
imwrite(x,map,'15_0.jpg','jpg');
figure;imshow('15_0.jpg')
>> info= imfinfo('15_0.jpg')
info =
Filename: '15_0.jpg'
FileModDate: '14-May-2009 13:03:42'
FileSize: 156287
Format: 'jpg'
FormatVersion: ''
Width: 700
Height: 525
BitDepth: 24
ColorType: 'truecolor'
FormatSignature: ''
NumberOfSamples: 3
CodingMethod: 'Huffman'
CodingProcess: 'Sequential'
Comment: {} 虽然是真彩,但是图像发生改变 先前的 15_0.jpg
>> imwrite(x,'15_0.jpg','jpg');
>> info= imfinfo('15_0.jpg')
info =
Filename: '15_0.jpg'
FileModDate: '14-May-2009 13:07:32'
FileSize: 10196
Format: 'jpg'
FormatVersion: ''
Width: 700
Height: 525
BitDepth: 8
ColorType: 'grayscale'
FormatSignature: ''
NumberOfSamples: 1
CodingMethod: 'Huffman'
CodingProcess: 'Sequential'
Comment: {}
事实证实,在imwrite中,参数设定不当,无法保存转换后的图像类型
以下可以验证:
第二次 imwrite后生成的 15_0.jpg
>> i=imread(('15_0.jpg');
??? i=imread(('15_0.jpg');
|
Error: Expression or statement is incorrect--possibly unbalanced (, {, or [.
>> i=imread('15_0.jpg');
>> t=isgray(i);
Warning: isgray is obsolete and may be removed in the future.
See product release notes for more information.
> In isgray at 27
>> t
t =
1
>> y=isrgb(i);
Warning: isrgb is obsolete and may be removed in the future.
See product release notes for more information.
> In isrgb at 29
>> y
y =
0
>>
另一个实验:
rgb=imread('17.bmp');
imshow(rgb);
[x1_no_dither,map]=rgb2ind(rgb,8,'nodither');
[x1_dither,map]=rgb2ind(rgb,8,'dither');
figure ,imshow(x1_no_dither,map);
figure ,imshow(x1_dither,map);
[rgb,map]=imread('17.bmp');
x2=rgb2gray(rgb);
newmap=rgb2gray(map);
figure,imshow(rgb,map);
figure,imshow(rgb,newmap);
figure ,imhsow(x2);
figure,imhsow(x2,newmap);
出错了地方,原因在于这里
>> newmap=rgb2gray(map);
??? Error using ==> rgb2gray>parse_inputs
MAP must be a m x 3 array.
Error in ==> rgb2gray at 35
X = parse_inputs(varargin{:});
>> info=imfinfo('17.bmp');
>> info
Width: 450
Height: 338
BitDepth: 24 这是24位的图像宽度.
ColorType: 'truecolor'
解决帮法是,位的转换,把24位图像转换位16位的图像,
先换一幅8位的gif图像:
>> info=imfinfo('canoe.gif');
>> info
info =
Filename: 'canoe.gif'
FileModDate: '14-May-2009 13:56:38'
FileSize: 241368
Format: 'GIF'
FormatVersion: '89a'
Width: 764
Height: 555
BitDepth: 8
ColorType: 'indexed'
FormatSignature: 'GIF89a'
BackgroundColor: 0
AspectRatio: 0
ColorTable: [256x3 double]
Interlaced: 'yes'
由于它是indexed图像,所以还需转换成真彩图像,
灰度图像转化位索引图像，８比特
>> i=imread('5.jpg');
subplot(121);
imshow(i);
title('原灰度图像')
subplot (122);
[x,map]=gray2ind(i,6);
imshow(x,map);
title('转换后的图像')
>> bw=dither(i);
>> imshow(bw);
>> title('转换后的二值图像')
>> [x,map]=imread('apple.jpg');
>> newmap=rgb2gray(map);
??? Error using ==> rgb2gray>parse_inputs
MAP must be a m x 3 array.
Error in ==> rgb2gray at 35
X = parse_inputs(varargin{:});
>>
这个错误：
Error using ==> rgb2gray>parse_inputs MAP must be a m x 3 array.
>> figure(1),imshow(x);
>> J=rgb2gray(x);
>> figure(2),imshow(J);
>>