Matlab image to matrix

Matlab image to matrix DEFAULT

how to convert an image to a matrix of pixels?

LOTS of stuff wrong with that code.

It's advisable not to have gigantic chunks of code in functions like fprintf(). Split it up into smaller parts so you can check each. At least onto separate lines. You have virtually a whole program in the argument list of printf()!

There is no function printf() - perhaps you means sprintf() or fprintf() instead.

Things like *X by themselves will cause an error.

You need to use single quotes in MATLAB to define a string, not double quotes.

Don't useimage as the name of your variable because that is the name of a built-in function.

What your college adviser told you does not make sense, or you did not convey it correctly. What does "decelerate the array" mean??? And I don't know what each of the 4 steps is supposed to accomplish. It just looks like a random set of tasks. Why do you need to compile this? Are you going to deploy it as a standalone executable or a libary file? Do you have the MATLAB Compiler? Since he seems to think he knows how to solver your problem (and we don't), can you sit down shoulder to shoulder with him until you have this all worked out?

Sours: https://www.mathworks.com/matlabcentral/answers/259673-how-to-convert-an-image-to-a-matrix-of-pixels

mat2gray

Read an image and display it.

I = imread('rice.png'); figure imshow(I)

Perform an operation that returns a numeric matrix. This operation looks for edges.

J = filter2(fspecial('sobel'),I); min_matrix = min(J(:))

Note that the matrix has data type with values outside of the range [0,1], including negative values.

Display the result of the operation. Because the data range of the matrix is outside the default display range of , every pixel with a positive value displays as white, and every pixel with a negative or zero value displays as black. It is challenging to see the edges of the grains of rice.

Convert the matrix into an image. Display the maximum and minimum values of the image.

K = mat2gray(J); min_image = min(K(:))

Note that values are still data type , but that all values are in the range [0, 1].

Display the result of the conversion. Pixels show a range of grayscale colors, which makes the location of the edges more apparent.

Sours: https://www.mathworks.com/help/images/ref/mat2gray.html
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image

Main Content

Syntax

Description

example

displays the data in array as an image. Each element of specifies the color for 1 pixel of the image. The resulting image is an -by- grid of pixels where is the number of rows and is the number of columns in . The row and column indices of the elements determine the centers of the corresponding pixels.

example

specifies the image location. Use and to specify the locations of the corners corresponding to and . To specify both corners, set and as two-element vectors. To specify the first corner and let determine the other, set and as scalar values. The image is stretched and oriented as applicable.

specifies the image location. This syntax is the low-level version of .

example

specifies image properties using one or more name-value pair arguments. You can specify image properties with any of the input argument combinations in the previous syntaxes.

creates the image in the axes specified by instead of in the current axes (). The option can precede any of the input argument combinations in the previous syntaxes.

example

returns the object created. Use to set properties of the image after it is created. You can specify this output with any of the input argument combinations in the previous syntaxes. For a list of image properties and descriptions, see Image Properties.

Examples

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Display Image of Matrix Data

Create matrix . Display an image of the data in . Add a colorbar to the graph to show the current colormap.

C = [0 2 4 6; 8 10 12 14; 16 18 20 22]; image(C) colorbar

By default, the property for the image is set to so interprets values in as indices into the colormap. For example, the bottom right pixel corresponding to the last element in , 22, uses the 22nd color of the colormap.

Scale the values to the full range of the current colormap by setting the property to when creating the image.

image(C,'CDataMapping','scaled') colorbar

Alternatively, you can use the function to scale the values instead of using . For example, use .

Control Image Placement

Place the image so that it lies between 5 and 8 on the x-axis and between 3 and 6 on the y-axis.

x = [5 8]; y = [3 6]; C = [0 2 4 6; 8 10 12 14; 16 18 20 22]; image(x,y,C)

Notice that the pixel corresponding to C(1,1) is centered over the point (5,3). The pixel corresponding to C(3,4) is centered over the point (8,6). positions and orients the rest of the image between those two points.

Display Image of 3-D Array of True Colors

Create as a 3-D array of true colors. Use only red colors by setting the last two pages of the array to zeros.

C = zeros(3,3,3); C(:,:,1) = [.1 .2 .3; .4 .5 .6; .7 .8 .9]
C = C(:,:,1) = 0.1000 0.2000 0.3000 0.4000 0.5000 0.6000 0.7000 0.8000 0.9000 C(:,:,2) = 0 0 0 0 0 0 0 0 0 C(:,:,3) = 0 0 0 0 0 0 0 0 0

Display an image of the data in .

Modify Image After Creation

Plot a line, and then create an image on top of the line. Return the image object.

plot(1:3) hold on C = [1 2 3; 4 5 6; 7 8 9]; im = image(C);

Make the image semitransparent so that the line shows through the image.

Read and Display JPEG Image File

Read a JPEG image file.

C = imread('ngc6543a.jpg');

returns a 650-by-600-by-3 array, .

Display the image.

Add Image to Axes in 3-D View

Create a surface plot. Then, add an image under the surface. displays the image in the xy-plane.

Z = 10 + peaks; surf(Z) hold on image(Z,'CDataMapping','scaled')

Input Arguments

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— Image color data
vector or matrix | 3-D array of RGB triplets

Image color data, specified in one of these forms:

  • Vector or matrix — This format defines indexed image data. Each element of defines a color for 1 pixel of the image. For example, . The elements of map to colors in the colormap of the associated axes. The property controls the mapping method.

  • 3-D array of RGB triplets — This format defines true color image data using RGB triplet values. Each RGB triplet defines a color for 1 pixel of the image. An RGB triplet is a three-element vector that specifies the intensities of the red, green, and blue components of the color. The first page of the 3-D array contains the red components, the second page contains the green components, and the third page contains the blue components. Since the image uses true colors instead of colormap colors, the property has no effect.

    • If is of type , then an RGB triplet value of corresponds to black and corresponds to white.

    • If is an integer type, then the image uses the full range of data to determine the color. For example, if is of type , then corresponds to black and corresponds to white. If is of type , then corresponds to black and corresponds to white.

    • If is of type , then corresponds to black and corresponds to white.

This illustration shows the relative dimensions of for the two color models.

The behavior of elements is not defined.

To use the low-level version of the function instead, set the property as a name-value pair. For example, .

Converting Between and Integer Data Types

When you call the function with a vector or 2-D matrix and use the default value, you must offset your data values by 1 when converting between values and integer types. This offset is not necessary when is set to .

For example, if contains indexed image data of type , you can convert it to type using:

To convert indexed image data from type to an integer type, subtract 1 and use to ensure that all the values are integers. For example, if contains indexed image data of type , convert it to using:

U8 = uint8(round(D - 1));

Converting Between Normalized and Truecolor Values

To convert true color image data from an integer type to type , rescale the data. For example, if is true color image data of type , convert it to using:

To convert true color image data from type to an integer type, rescale the data and use to ensure that all the values are integers. For example, if is image data of type , convert it to using:

RGB8 = uint8(round(RGB*255));

Data Types: | | | | | | | | | |

— Placement along x-axis
(default) | two-element vector | scalar

Placement along the x-axis, specified in one of these forms:

  • Two-element vector — Use the first element as the location for the center of and the second element as the location for the center of , where . If is a 3-D array, then and are the first two dimensions. Evenly distribute the centers of the remaining elements of between those two points.

    The width of each pixel is determined by the expression:

    (x(2)-x(1))/(size(C,2)-1)

    If > , then the image is flipped left-right.

  • Scalar — Center at this location and each following element one unit apart.

To use the low-level version of the function instead, set the property as a name-value pair. For example, .

You cannot interactively pan or zoom outside the x-axis limits or y-axis limits of an image, unless the limits are already set outside the bounds of the image. If the limits are already outside the bounds, there is no such restriction. If other objects (such as a line) occupy the axes and extend beyond the bounds of the image, you can pan or zoom to the bounds of the other objects, but no further.

Data Types: | | | | | | | | | |

— Placement along y-axis
(default) | two-element vector | scalar

Placement along y-axis, specified in one of these forms:

  • Two-element vector — Use the first element as the location for the center of and the second element as the location for the center of , where . If is a 3-D array, then and are the first two dimensions. Evenly distribute the centers of the remaining elements of between those two points.

    The height of each pixel is determined by the expression:

    (y(2)-y(1))/(size(C,1)-1)

    If > , then the image is flipped up-down.

  • Scalar — Center at this location and each following element one unit apart.

To use the low-level version of the function instead, set the property as a name-value pair. For example, .

You cannot interactively pan or zoom outside the x-axis limits or y-axis limits of an image, unless the limits are already set outside the bounds of the image. If the limits are already outside the bounds, there is no such restriction. If other objects (such as a line) occupy the axes and extend beyond the bounds of the image, you can pan or zoom to the bounds of the other objects, but no further.

Data Types: | | | | | | | | | |

— object
object

object. If you do not specify an object, then uses the current axes.

Name-Value Arguments

Specify optional comma-separated pairs of arguments. is the argument name and is the corresponding value. must appear inside quotes. You can specify several name and value pair arguments in any order as .

Example: displays a semitransparent image.

The properties listed here are a subset of image properties. For a complete list, see Image Properties.

— Color data mapping method
(default) |

Color data mapping method, specified as or . Use this property to control the mapping of color data values in into the colormap. must be a vector or a matrix defining indexed colors. This property has no effect if is a 3-D array defining true colors.

The methods have these effects:

  • — Interpret the values as indices into the current colormap. Values with a decimal portion are fixed to the nearest lower integer.

    • If the values are of type or , then values of or less map to the first color in the colormap. Values equal to or greater than the length of the colormap map to the last color in the colormap.

    • If the values are of type , , , , , , , or , then values of or less map to the first color in the colormap. Values equal to or greater than the length of the colormap map to the last color in the colormap (or up to the range limits of the type).

    • If the values are of type , then values of map to the first color in the colormap and values of map to the second color in the colormap.

  • — Scale the values to range between the minimum and maximum color limits. The property of the axes contains the color limits.

— Transparency data
(default) | scalar | array the same size as

Transparency data, specified in one of these forms:

  • Scalar — Use a consistent transparency across the entire image.

  • Array the same size as — Use a different transparency value for each image element.

The property controls how MATLAB® interprets the alpha data transparency values.

Example:

Data Types: | | | | | | | | | |

— Interpretation of values
(default) | |

Interpretation of values, specified as one of these values:

  • — Interpret the values as transparency values. A value of 1 or greater is completely opaque, a value of 0 or less is completely transparent, and a value between 0 and 1 is semitransparent.

  • — Map the values into the figure’s alphamap. The minimum and maximum alpha limits of the axes determine the alpha data values that map to the first and last elements in the alphamap, respectively. For example, if the alpha limits are , then alpha data values less than or equal to map to the first element in the alphamap. Alpha data values greater than or equal to map to the last element in the alphamap. The property of the axes contains the alpha limits. The property of the figure contains the alphamap.

  • — Interpret the values as indices into the figure’s alphamap. Values with a decimal portion are fixed to the nearest lower integer:

    • If the values are of type or , then values of 1 or less map to the first element in the alphamap. Values equal to or greater than the length of the alphamap map to the last element in the alphamap.

    • If the values are of type integer, then values of 0 or less map to the first element in the alphamap. Values equal to or greater than the length of the alphamap map to the last element in the alphamap (or up to the range limits of the type). The integer types are , , , , , , , and .

    • If the values are of type , then values of 0 map to the first element in the alphamap and values of 1 map to the second element in the alphamap.

Output Arguments

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— object
object

object, returned as a scalar. Use to set properties of the image after it is created. For a list, see Image Properties.

More About

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High-Level Versus Low-Level Version of Image

The function has two versions, the high-level version and the low-level version. If you use with as an input argument, then you are using the low-level version. Otherwise, you are using the high-level version.

The high-level version of calls before plotting and sets these axes properties:

  • to . The image is shown in front of any tick marks or grid lines.

  • to . Values along the y-axis increase from top to bottom. To decrease the values from top to bottom, set to . This setting reverses both the y-axis and the image.

  • to .

The low-level version of the function does not call and does not set these axes properties.

Tips

  • To read image data into MATLAB from graphics files in various standard formats, such as TIFF, use . To write MATLAB image data to graphics files, use . The and functions support a variety of graphics file formats and compression schemes.

Extended Capabilities

GPU Arrays
Accelerate code by running on a graphics processing unit (GPU) using Parallel Computing Toolbox™.

Usage notes and limitations:

  • This function accepts GPU arrays, but does not run on a GPU.

For more information, see Run MATLAB Functions on a GPU (Parallel Computing Toolbox).

Distributed Arrays
Partition large arrays across the combined memory of your cluster using Parallel Computing Toolbox™.

Usage notes and limitations:

  • This function operates on distributed arrays, but executes in the client MATLAB.

For more information, see Run MATLAB Functions with Distributed Arrays (Parallel Computing Toolbox).

See Also

Functions

Properties

Introduced before R2006a

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Sours: https://www.mathworks.com/help/matlab/ref/image.html

How to convert matrix into image ?

a = imread('Rose-flower.jpg');

subplot(2,3,1);

imshow(a);

c = rgb2gray(a);

subplot(2,3,2);

imshow(c)

% Class Task:

h =[1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20,

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20,

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20,

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20,

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20,

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20,

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20,

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20,

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20,

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20,

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20,

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20,

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20,

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20,

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20,

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20,

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20,

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20,

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20,

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20];

imshow(h)

i = uint8(h);

imshow(i)

i do not understand that how to get image in using matrix....what is reason...? You can fix code...

Sours: https://www.mathworks.com/matlabcentral/answers/375555-how-to-convert-matrix-into-image

Image to matrix matlab

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Convert Image into Matrix - Like a Pro!

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Now discussing:

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