2+2 ans = 4 a=2 a = 2 a a = 2 a=2; a a = 2 b=zeros(5) b = 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 b=zeros(5,1) b = 0 0 0 0 0 a= [1 2 3 ] a = 1 2 3 a a = 1 2 3 a' ans = 1 2 3 b = 1:5; b b = 1 2 3 4 5 1:25 ans = Columns 1 through 11 1 2 3 4 5 6 7 8 9 10 11 Columns 12 through 22 12 13 14 15 16 17 18 19 20 21 22 Columns 23 through 25 23 24 25 c = 1:3:20 c = 1 4 7 10 13 16 19 d = 1:3.5:20 d = 1.0000 4.5000 8.0000 11.5000 15.0000 18.5000 clc e = rand(10,1) e = 0.8147 0.9058 0.1270 0.9134 0.6324 0.0975 0.2785 0.5469 0.9575 0.9649 f = randn(15,1) f = -1.3499 3.0349 0.7254 -0.0631 0.7147 -0.2050 -0.1241 1.4897 1.4090 1.4172 0.6715 -1.2075 0.7172 1.6302 0.4889 hist(randn(10000,1),200) a=randn(10000,1); min(a) ans = -3.9157 max(a) ans = 4.0904 a= rand(10,10) a = Columns 1 through 8 0.4681 0.8492 0.2788 0.0538 0.3942 0.1035 0.8513 0.7036 0.5686 0.6386 0.7141 0.1484 0.6044 0.3992 0.9643 0.6507 0.9153 0.4979 0.0981 0.0805 0.9963 0.5377 0.5367 0.8682 0.4166 0.9216 0.9140 0.7115 0.1278 0.2159 0.8876 0.3478 0.0888 0.3472 0.7847 0.0700 0.1980 0.3857 0.7497 0.3306 0.7675 0.0221 0.1518 0.5241 0.8878 0.9138 0.1397 0.2938 0.3721 0.0483 0.4211 0.7782 0.0602 0.3621 0.0046 0.0133 0.4885 0.7962 0.9548 0.0715 0.0833 0.5417 0.7913 0.2797 0.2929 0.9709 0.1895 0.6613 0.5858 0.1828 0.5140 0.8578 0.6122 0.7417 0.2734 0.4349 0.0379 0.3415 0.2310 0.1511 Columns 9 through 10 0.5525 0.5824 0.0610 0.5865 0.8462 0.4205 0.9628 0.8331 0.3011 0.1552 0.2332 0.1093 0.9351 0.5232 0.8421 0.5528 0.7798 0.1637 0.5076 0.1494 a= rand(8,8) a = 0.0603 0.8492 0.2024 0.4907 0.9713 0.4480 0.7463 0.9890 0.4325 0.4206 0.7560 0.3657 0.6318 0.9403 0.5868 0.8064 0.4899 0.8110 0.9443 0.6138 0.4059 0.9786 0.3030 0.0430 0.0053 0.9899 0.8605 0.6534 0.4438 0.4922 0.5851 0.5424 0.2614 0.4332 0.4067 0.2140 0.0068 0.4417 0.5749 0.2647 0.3426 0.9622 0.9514 0.5587 0.3348 0.7977 0.2065 0.5091 0.0135 0.4352 0.4692 0.9563 0.7695 0.1205 0.0571 0.5821 0.7008 0.2074 0.7073 0.8838 0.6461 0.8274 0.2295 0.0456 imagesc(a) colormap('gray') a(1,2) ans = 0.8492 a(1:3,1:3) ans = 0.0603 0.8492 0.2024 0.4325 0.4206 0.7560 0.4899 0.8110 0.9443 figure(2) imagesc(a(1:3,1:3)) colormap(gray) gray ans = 0 0 0 0.0159 0.0159 0.0159 0.0317 0.0317 0.0317 0.0476 0.0476 0.0476 0.0635 0.0635 0.0635 0.0794 0.0794 0.0794 0.0952 0.0952 0.0952 0.1111 0.1111 0.1111 0.1270 0.1270 0.1270 0.1429 0.1429 0.1429 0.1587 0.1587 0.1587 0.1746 0.1746 0.1746 0.1905 0.1905 0.1905 0.2063 0.2063 0.2063 0.2222 0.2222 0.2222 0.2381 0.2381 0.2381 0.2540 0.2540 0.2540 0.2698 0.2698 0.2698 0.2857 0.2857 0.2857 0.3016 0.3016 0.3016 0.3175 0.3175 0.3175 0.3333 0.3333 0.3333 0.3492 0.3492 0.3492 0.3651 0.3651 0.3651 0.3810 0.3810 0.3810 0.3968 0.3968 0.3968 0.4127 0.4127 0.4127 0.4286 0.4286 0.4286 0.4444 0.4444 0.4444 0.4603 0.4603 0.4603 0.4762 0.4762 0.4762 0.4921 0.4921 0.4921 0.5079 0.5079 0.5079 0.5238 0.5238 0.5238 0.5397 0.5397 0.5397 0.5556 0.5556 0.5556 0.5714 0.5714 0.5714 0.5873 0.5873 0.5873 0.6032 0.6032 0.6032 0.6190 0.6190 0.6190 0.6349 0.6349 0.6349 0.6508 0.6508 0.6508 0.6667 0.6667 0.6667 0.6825 0.6825 0.6825 0.6984 0.6984 0.6984 0.7143 0.7143 0.7143 0.7302 0.7302 0.7302 0.7460 0.7460 0.7460 0.7619 0.7619 0.7619 0.7778 0.7778 0.7778 0.7937 0.7937 0.7937 0.8095 0.8095 0.8095 0.8254 0.8254 0.8254 0.8413 0.8413 0.8413 0.8571 0.8571 0.8571 0.8730 0.8730 0.8730 0.8889 0.8889 0.8889 0.9048 0.9048 0.9048 0.9206 0.9206 0.9206 0.9365 0.9365 0.9365 0.9524 0.9524 0.9524 0.9683 0.9683 0.9683 0.9841 0.9841 0.9841 1.0000 1.0000 1.0000 figure(1) colormap('jet') rampImage=1:64 rampImage = Columns 1 through 14 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Columns 15 through 28 15 16 17 18 19 20 21 22 23 24 25 26 27 28 Columns 29 through 42 29 30 31 32 33 34 35 36 37 38 39 40 41 42 Columns 43 through 56 43 44 45 46 47 48 49 50 51 52 53 54 55 56 Columns 57 through 64 57 58 59 60 61 62 63 64 figure imagesc(rampImage) colormap(gray) a=[1 2 ; 3 4] a = 1 2 3 4 a(:) ans = 1 3 2 4 eye(5) ans = 1 0 0 0 0 0 1 0 0 0 0 0 1 0 0 0 0 0 1 0 0 0 0 0 1 who Your variables are: a b d f ans c e rampImage whos Name Size Bytes Class Attributes a 2x2 32 double ans 5x5 200 double b 1x5 40 double c 1x7 56 double d 1x6 48 double e 10x1 80 double f 15x1 120 double rampImage 1x64 512 double size(a) ans = 2 2 help imread IMREAD Read image from graphics file. A = IMREAD(FILENAME,FMT) reads a grayscale or color image from the file specified by the string FILENAME. If the file is not in the current directory, or in a directory on the MATLAB path, specify the full pathname. The text string FMT specifies the format of the file by its standard file extension. For example, specify 'gif' for Graphics Interchange Format files. To see a list of supported formats, with their file extensions, use the IMFORMATS function. If IMREAD cannot find a file named FILENAME, it looks for a file named FILENAME.FMT. The return value A is an array containing the image data. If the file contains a grayscale image, A is an M-by-N array. If the file contains a truecolor image, A is an M-by-N-by-3 array. For TIFF files containing color images that use the CMYK color space, A is an M-by-N-by-4 array. See TIFF in the Format-Specific Information section for more information. The class of A depends on the bits-per-sample of the image data, rounded to the next byte boundary. For example, IMREAD returns 24-bit color data as an array of uint8 data because the sample size for each color component is 8 bits. See the Remarks section for a discussion of bitdepths, and see the Format-Specific Information section for more detail about supported bitdepths and sample sizes for a particular format. [X,MAP] = IMREAD(FILENAME,FMT) reads the indexed image in FILENAME into X and its associated colormap into MAP. Colormap values in the image file are automatically rescaled into the range [0,1]. [...] = IMREAD(FILENAME) attempts to infer the format of the file from its content. [...] = IMREAD(URL,...) reads the image from an Internet URL. The URL must include the protocol type (e.g., "http://"). Remarks Bitdepth is the number of bits used to represent each image pixel. Bitdepth is calculated by multiplying the bits-per-sample with the samples-per-pixel. Thus, a format that uses 8-bits for each color component (or sample) and three samples per pixel has a bitdepth of 24. Sometimes the sample size associated with a bitdepth can be ambiguous: does a 48-bit bitdepth represent six 8-bit samples or three 16-bit samples? The following format-specific sections provide sample size information to avoid this ambiguity. Format-Specific Information (Listed Alphabetically by Format) BMP -- Windows Bitmap Supported Compression Output Bitdepths None RLE Class Notes --------------------------------------------------------- 1-bit x - logical 4-bit x x uint8 8-bit x x uint8 16-bit x - uint8 1 sample/pixel 24-bit x - uint8 3 samples/pixel 32-bit x - uint8 3 samples/pixel (1 byte padding) CUR -- Cursor File Supported Compression Output Bitdepths None Compressed Class -------------------------------------------------- 1-bit x - logical 4-bit x - uint8 8-bit x - uint8 Special syntaxes: [...] = IMREAD(...,IDX) reads in one image from a multi-image icon or cursor file. IDX is an integer value that specifies the order that the image appears in the file. For example, if IDX is 3, IMREAD reads the third image in the file. If you omit this argument, IMREAD reads the first image in the file. [A,MAP,ALPHA] = IMREAD(...) returns the AND mask for the resource, which can be used to determine transparency information. For cursor files, this mask may contain the only useful data. GIF -- Graphics Interchange Format Supported Compression Output Bitdepths None Compressed Class --------------------------------------------- 1-bit x - logical 2-to-8 bit x - uint8 Special syntaxes: [...] = IMREAD(...,IDX) reads in one or more frames from a multiframe (i.e., animated) GIF file. IDX must be an integer scalar or vector of integer values. For example, if IDX is 3, IMREAD reads the third image in the file. If IDX is 1:5, only the first five frames are returned. [...] = IMREAD(...,'Frames',IDX) is the same as the syntax above except that IDX can be 'all'. In this case, all of the frames are read and returned in the order that they appear in the file. Note: Because of the way GIF files are structured, all of the frames must be read when a particular frame is requested. Consequently, it is much faster to specify a vector of frames or 'all' for IDX than to call IMREAD in a loop when reading multiple frames from the same GIF file. HDF -- Hierarchical Data Format Supported Raster image Raster image Output Bitdepths with colormap without colormap Class Notes ------------------------------------------------------------ 8-bit x x uint8 24-bit - x uint8 3 samples/pixel Special Syntaxes: [...] = IMREAD(...,REF) reads in one image from a multi-image HDF file. REF is an integer value that specifies the reference number used to identify the image. For example, if REF is 12, IMREAD reads the image whose reference number is 12. (Note that in an HDF file the reference numbers do not necessarily correspond with the order of the images in the file. You can use IMFINFO to match up image order with reference number.) If you omit this argument, IMREAD reads the first image in the file. ICO -- Icon File See CUR. JPEG -- Joint Photographic Experts Group Note: IMREAD can read any baseline JPEG image as well as JPEG images with some commonly used extensions. Supported Compression Output Bitdepths Lossy Lossless Class Notes -------------------------------------------------------- 8-bit x x uint8 Grayscale or RGB 12-bit x x uint16 Grayscale 16-bit - x uint16 Grayscale 36-bit x x uint16 RGB(Three 12-bit samples/pixel) JPEG 2000 - Joint Photographic Experts Group 2000 Supported Compression Output Bitdepths Lossy Lossless Class Notes (per sample) ---------------------------------------------------------- 1-bit x x logical Grayscale only 2- to 8-bit x x uint8 Grayscale or RGB 9- to 16-bit x x uint16 Grayscale or RGB Note: Only 1- and 3-sample images are supported. Indexed JPEG 2000 images are not supported. Special Syntaxes [...] = IMREAD(..., 'Param1', value1, 'Param2', value2, ...) uses parameter-value pairs to control the read operation. There are two different parameters you can use: Parameter name Value -------------- ----- 'ReductionLevel' A non-negative integer specifying reduction in the resolution of the image. For a reduction level 'L', the image resolution is reduced by a factor of 2^L. Its default value is 0 implying no reduction. The reduction level is limited by the total number of decomposition levels as provided by 'WaveletDecompositionLevels' field in the structure returned from IMFINFO function. 'PixelRegion' {ROWS, COLS}. IMREAD returns the sub-image specified by the boundaries in ROWS and COLS. ROWS and COLS must both be two-element vectors that denote the 1-based indices [START STOP]. If 'ReductionLevel' is greater than 0, then ROWS and COLS are coordinates in the reduced-sized image. PBM -- Portable Bitmap Supported Raw ASCII (Plain) Output Bitdepths Binary Encoded Class ---------------------------------------- 1-bit x x logical PCX -- Windows Paintbrush Supported Output Bitdepths Class Notes ---------------------------------------------- 1-bit logical Grayscale only 8-bit uint8 Grayscale or indexed 24-bit uint8 RGB (8-bit samples) PGM -- Portable Graymap Supported Raw ASCII (Plain) Output Bitdepths Binary Encoded Class ------------------------------------------------ up to 16-bit x - uint8 Arbitrary - x PNG -- Portable Network Graphics Supported Output Bitdepths Class Notes ------------------------------------------- 1-bit logical Grayscale only 2-bit uint8 Grayscale only 4-bit uint8 Grayscale only 8-bit uint8 Grayscale or Indexed 16-bit uint16 Grayscale or Indexed 24-bit uint8 RGB (Three 8-bit samples/pixel) 48-bit uint16 RGB (Three 16-bit samples/pixel) Special Syntaxes: [...] = IMREAD(...,'BackgroundColor',BG) composites any transparent pixels in the input image against the color specified in BG. If BG is 'none', then no compositing is performed. Otherwise, if the input image is indexed, BG should be an integer in the range [1,P] where P is the colormap length. If the input image is grayscale, BG should be an integer in the range [0,1]. If the input image is RGB, BG should be a three-element vector whose values are in the range [0,1]. The string 'BackgroundColor' may be abbreviated. If the ALPHA output argument is used (see below), then BG defaults to 'none' if not specified by the user. Otherwise, if the PNG file ontains a background color chunk, that color is used as the default value for BG. If ALPHA is not used and the file does not contain a background color chunk, then the default value for BG is 1 for indexed images; 0 for grayscale images; and [0 0 0] for RGB images. [A,MAP,ALPHA] = IMREAD(...) returns the alpha channel if one is present; otherwise ALPHA is []. Note that MAP may be empty if the file contains a grayscale or truecolor image. PPM -- Portable Pixmap Supported Raw ASCII (Plain) Output Bitdepths Binary Encoded Class ------------------------------------------------ up to 16-bit x - uint8 Arbitrary - x RAS -- Sun Raster Supported Output Bitdepths Class Notes ---------------------------------------------------- 1-bit logical Bitmap 8-bit uint8 Indexed 24-bit uint8 RGB (8-bit samples) 32-bit uint8 RGB with Alpha (8-bit samples) TIFF -- Tagged Image File Format Supported Compression Output Bitdepths None Packbits CCITT RGB ICCLAB CIELAB CMYK Class Notes ----------------------------------------------------------------------- 1-bit x x x - - - - logical 8-bit x x - - - - - uint8 12-bit - - - - - - - uint16 Grayscale or Indexed 16-bit - - - - - - - uint16 Grayscale or Indexed 24-bit x x - x x x - uint8 3 samples 32-bit - - - - - - x uint8 4 samples 36-bit - - - x - - - uint16 3 samples 48-bit - - - x x x - uint16 3 samples 64-bit - - - - - - x double 4 samples NOTE: IMREAD supports 8-bit integral and 32-bit floating point tiled TIFF images, with any compression and colorspace combination listed above, and 32-bit IEEE floating point images. Special Syntaxes: A = IMREAD(...) returns color data that uses the RGB, CIELAB, ICCLAB, or CMYK color spaces. If the color image uses the CMYK color space, A is an M-by-N-by-4 array. [...] = IMREAD(..., 'Param1', value1, 'Param2', value2, ...) uses parameter-value pairs to control the read operation. There are three different parameters you can use: Parameter name Value -------------- ----- 'Index' A positive integer specifying which image to read in a multi-image TIFF file. For example, if 'Index' is 3, IMREAD reads the third image in the file. 'Info' A structure array; the output of IMFINFO. When reading images from a multi-image TIFF file, passing the output of IMFINFO as the 'Info' parameter helps IMREAD locate the images in the file more quickly. 'PixelRegion' {ROWS, COLS}. IMREAD returns the sub-image specified by the boundaries in ROWS and COLS. ROWS and COLS must be either two- or three-element vectors. If two elements are provided, they denote the 1-based indices [START STOP]. If three elements are provided, the indices [START INCREMENT STOP] allow image downsampling. XWD -- X Window Dump Supported Output Bitdepths ZPixmaps XYBitmaps XYPixmaps Class -------------------------------------------------- 1-bit x - x logical 8-bit x - - uint8 See also imfinfo, imwrite, imformats, fread, image, double, uint8. Reference page in Help browser doc imread im=imread('flower.tiff') im(:,:,1) = Columns 1 through 17 91 93 95 96 95 96 97 96 96 89 89 85 84 83 83 80 79 88 91 92 93 94 95 94 94 93 91 90 85 83 83 81 77 73 ... I deleted the output from here to the end of the image, as it is too big... (- Erik). 26 25 25 28 30 28 28 im=imread('flower.tiff'); imagesc(im) size(im) ans = 333 500 3 im(1,1,:) ans(:,:,1) = 91 ans(:,:,2) = 112 ans(:,:,3) = 45 im(1,1,:)/256 ans(:,:,1) = 0 ans(:,:,2) = 0 ans(:,:,3) = 0 double(im(1,1,:))/256 ans(:,:,1) = 0.3555 ans(:,:,2) = 0.4375 ans(:,:,3) = 0.1758 lookfor fourier fft - Discrete Fourier transform. fft2 - Two-dimensional discrete Fourier Transform. fftn - N-dimensional discrete Fourier Transform. ifft - Inverse discrete Fourier transform. ifft2 - Two-dimensional inverse discrete Fourier transform. ifftn - N-dimensional inverse discrete Fourier transform. diary off