Get Started with Image Tool

The Image Tool presents an integrated environment for displaying images and performing common image processing tasks. The workflow for using Image Tool typically involves a combination of these steps:

• Open the tool and display an image

• Navigate the image

• Get information about the image data

• Modify the image data

• Save and export results

Note

The Image Viewer app is recommended over Image Tool in most situations. Image Viewer offers more functionality and is easier to use than the Image Tool. Use the Image Tool only when you need to customize the figure containing the tool. For more information, see Get Started with Image Viewer App.

The figure shows an image displayed in an Image Tool with many of the related tools open and active.

Note

You can also access individual tools outside the Image Tool. To do so, display an image in a figure window using a function such as imshow, then create one or more tools using toolbox functions. For example, you can build an image processing app with custom layout and behavior using a combination of individual tools. For more information, see Interactive Tool Workflow

Open Image Tool and Display Image

There are three ways to open the Image Tool. In each case, you can select an image from a variable in the workspace or specify the name of the image file. Image Tool can open any file that can be read by imread.

• You can open the Image Tool from the command line by using the imtool function. You can control various aspects of the initial image display, such as the initial magnification, colormap, or display range. For example, this code opens Image Tool and loads the image with filename cameraman.tif.

  imtool("cameraman.tif")

• You can open the Image Tool from the command line by using the images.compatibility.imtool.r2023b.imtool function. Use this option to return the figure containing the Image Tool. For example, this code opens Image Tool, loads the image with filename cameraman.tif, and returns the figure containing the tool.

  hTool = images.compatibility.imtool.r2023b.imtool("cameraman.tif")

• You can start a new Image Tool from within an existing Image Tool by using the New option from the File menu.

Navigate Image in Image Tool

After you open Image Tool, the image appears in the figure window. Image Tool provides navigation aids and tools that can help you explore images in detail.

Action	Tools and Navigation Aids	Depiction of Tool
See image overview	The Overview tool displays the entire image with a superimposed detail rectangle that indicates which portion of the image is currently visible in Image Tool. You can pan and zoom the image visible in the Image Tool by moving and resizing the detail rectangle in the Overview tool. To get the current position and size of the detail rectangle, right-click anywhere inside the rectangle and select Copy Position from the context menu. The tool copies the position as a four-element vector of the form [xmin ymin width height] to the clipboard. To print the view of the image displayed in the Overview tool, select the Print to Figure option from the Overview tool File menu. See Print Images for more information.
Magnify image	To enlarge or shrink an image by specifying a scale factor, use the Magnification option on the Tools menu. To enlarge or shrink an image by clicking the image, use the Zoom tool. The tool centers the new view of the image on the spot where you clicked. Note You can also zoom by using the Ctrl+Plus or Ctrl+Minus keys. These are the Plus(+) and Minus(-) keys on the numeric keypad of your keyboard. When Image Tool scales an image, it uses interpolation to determine the values for screen pixels that do not directly correspond to elements in the image matrix. For more information about interpolation methods used for resizing images, see imresize.
Pan image	To pan an image that is too large to fit in the Image Tool, use scroll bars or the Pan tool.
Choose image colormap	To enhance the visibility of features in grayscale and indexed images, you can change the image colormap using the Choose Colormap tool. You can select a MATLAB® colormap or a colormap variable from the workspace. You can also create a colormap by entering a MATLAB command. Image Tool does not provide a color bar. To add a color bar, open the image in another figure window. For more information, see Save and Export Results.

Get Information about Image Data

Image Tool provides tools that can help you get information about pixel values and other aspects of the image data.

Tool	Description	Depiction of Tool
Pixel Information tool	Get the (x, y) coordinates and the value of a single pixel under the pointer. The format of the pixel information depends on the image type. To save the pixel location and value information, right-click a pixel in the image and choose the Copy pixel info option. The Image Tool copies the x- and y-coordinates and the pixel value to the clipboard. You can paste this pixel information into the workspace or another application.
Display Range tool	Determine the display range of grayscale image data. The tool is not enabled for RGB, indexed, or binary images. The display range is of the form [cmin cmax]. The cmin and cmax values specify the pixel intensities that map to the first and last colors in the colormap, respectively.
Pixel Region tool	Get information about a group of pixels. When the magnified pixels are sufficiently large, the Pixel Region tool overlays the pixel value over each pixel. For RGB images, this information includes three numeric values, one for each color channel. For indexed images, this information includes the index value and the associated RGB value. You can toggle the display of numeric pixel values by going to the Pixel Region tool Edit menu and changing the Superimpose Pixel Values option. The Pixel Region tool includes its own Pixel Information tool that enables you to get the (x, y) coordinates and pixel value of the pixel under the pointer in the Pixel Region tool. To save the position of the pixel region rectangle with respect to the image, select the Copy Position option from the Pixel Region tool Edit menu. The tool copies the position as a four-element vector of the form [xmin ymin width height] to the clipboard. To print the view of the image displayed in the Pixel Region tool, select the Print to Figure option from the Pixel Region tool File menu. See Print Images for more information.
Distance tool	Measure the Euclidean distance between two pixels. The Distance tool displays a line between the pixels and a label with the Euclidean distance between endpoints of the line. The tool specifies the distance in data units determined by the XData and YData properties, which is pixels, by default. To customize aspects of the Distance tool appearance and behavior, use the Distance tool context menu. For example, you can toggle the distance label on and off, change the color of the distance line, and constrain the tool to the vertical or horizontal direction. To create variables in the workspace for the endpoint locations and distance information, right-click the Distance tool and choose the Export to Workspace option from the context menu.
Image Information tool	Get information about image and image file metadata. The Image Information tool always provides basic information about the width, height, data type, and image type. For grayscale and indexed images, this information includes the minimum and maximum intensity values. If you select an image to open in Image Tool by specifying a filename, then the Image Information tool also displays image metadata. This metadata is the same information returned by the imfinfo function or the dicominfo function.

Modify Image Data

Image Tool provides tools that can help you adjust the image contrast and crop an image.

By default, when you close Image Tool, the tool does not save the modified image data. However, you can export the modified image to a file or save the modified data in a workspace variable. For more information, see Save and Export Results.

Tool	Description	Depiction of Tool
Adjust Contrast tool	Adjust the contrast of an image by setting a window over a histogram of pixel values. Open the Adjust Contrast tool by clicking Adjust Contrast in the Image Tool toolbar. You can adjust the display window by clicking and dragging on the edges of the red window, or by entering values in the boxes for the minimum, maximum, center, and width of the window. Alternatively, let the Adjust Contrast tool scale the display range automatically. Select Match data range to make the display range equal to the data range of the image. Select Eliminate outliers to saturate an equal percentage of pixels at the top and bottom of the display range. By default, the tool eliminates 2%, so the top 1% and the bottom 1% of pixel values.
Window/Level tool	Adjust the contrast of an image by interacting with the image. To start the Window/Level tool, click the Window/Level in the Image Tool toolbar or select the Window/Level option from the Image Tool Tools menu. Move the pointer over the image. The pointer changes to the Window/Level cursor . To adjust the image contrast, click and drag the mouse horizontally. To adjust image brightness, click and drag the mouse vertically.
Crop Image tool	Crop an image to a rectangular region of interest. Start the Crop Image tool by clicking Crop Image in the Image Tool toolbar or by selecting Crop Image from the Image Tool Tools menu. When you move the pointer over the image, the pointer changes to cross hairs . Define the rectangular crop region by clicking and dragging the mouse over the image. You can move or resize the crop rectangle using the mouse. Or, if you want to crop a different region, move to the new location and click and drag again. When you are finished defining the crop region, double-click the left mouse button to crop the image.

Save and Export Results

Image Tool enables you to export image data to the workspace, save the image data to file, and open images in a new figure window. When saving and exporting image data, changes to the display range are not preserved. If you would like to preserve your changes, then use the imcontrast function.

Destination	Procedure
Create workspace variable	There are three ways to create a workspace variable from the image data in Image Tool. You can use the Export to Workspace option on the Image Tool File menu. If you open the tool by using the imtool function and specify a handle to the tool, then you can use the getimage function and specify the handle to the tool. For example, this code opens the image with file name moon.tif in an Image Tool then exports the image to the variable moon. hTool = imtool("moon.tif"); moon = getimage(hTool); If you open the tool without specifying a handle to the tool, then you can use the getimage function and specify a handle to the image object within the figure. For example, this code opens the image with file name moon.tif in an Image Tool then exports the image to the variable moon. imtool("moon.tif") moon = getimage(imgca);
Save to file	Use the Save Image tool by selecting the Save as option on the Image Tool File menu. This tool enables you to navigate your file system to determine where to save the file, specify the file name, and choose the file format.
Open new figure window	Select the Print to Figure option from the File menu. You can use this figure window to see a color bar and print the image. For more information, see Add Color Bar to Displayed Grayscale Image and Print Images.