Saving a cropped high-resolution image

The images displayed by are extremely large composites called image hierarchies. They do not exist as a single file, but rather a collection of many small files at different resolutions. To present the desired image to the user, some of these small images are retrieved for contiguous display.

We have provided a tool to enable the user to obtain part of a desired image formed from an image hierarchy. The user may use this tool to crop part of an image and to save it to a local disk. The saved image will be a compressed JPEG suitable for editing, printing, or inclusion in a publication.

This tool is not intended to retrieve an entire image at its highest resolution. It has been tested and found satisfactory for retrieving cropped images of up to 6000x4800 pixels.

Note: Measurements in inches are used several times in this description. These dimensions are those at which the image will print if it is printed from an application that pays attention to image size such as Adobe Photoshop. The actual pixel dimensions of the image are found by multiplying its dimensions by the DPI.

Changes to this dialog box will reflect its use for retrieving cropped images.


Screen capture of a displayed image will yield a low resolution image of approximately 75dpi. To save a higher resolution image, the tool inspects the desired coordinates and retrieves data from higher resolution levels of the image hierarchy to fulfill the request.

The tool does not manufacture resolution; the underlying image hierarchy must contain the necessary data. How much real resolution is available for a saved image depends on the depth of the image hierarchy and the position of the currently displayed image in it.

In the following table, the first two columns show the relationship between the DPI control and the maximum magnification that should be used to crop an image. The remaining columns show actual values for a 5"x4" crop; because the image compression ratio depends on the nature of the image content, these values should be used as a guide only.

TABLE 1: Sample values for a 5"x4" crop at various DPIs and magnifications
DPI Maximum Suggested Magnification Dimensions Pixels Image size(B) File size(B)
75 100.00% 375x300 112K 340K 15K
150 50.00% 750x600 450K 1.4M 77K
300 25.00% 1500x1200 1.8M 5.4M 427K
600 12.50% 3000x2400 7.2M 21.6M 2.2M
1200 6.25% 6000x4800 28.8M 86.4M 8.4M

Step-by-Step Guide to Saving High-Resolution Images

The steps to save a cropped image are simple.

  1. Start the Java annotator for the desired image (by clicking on the icon next to image thumbnail)
  2. From the Right-click menu, select "Save printable image"
  3. Choose the desired image resolution
  4. Use the file browser to specify the file name
  5. Draw the selection rectangle on the image
  6. Save the image and close the annotator
These steps are described in more detail below.

1. Start the annotator for the desired image

From the home page, select the desired species under the Datasets heading on the left of the page. Next, click on the desired series of slides. Then click on the appropriate Java symbol (the icon to the right of the desired slide number) to start the annotator. Prior to its running, click Trust on the Verify Certificate dialog. The annotator will then open, and the image may be moved to the desired area and magnification. After the image is shown as desired, right click on the image and choose Save printable image. A new dialog looking like the following will be displayed. Subsequent description will refer to areas on this dialog.

2. Select "Save printable image" from the Right-click menu

The Right-click menu is shown in the figure below; select "Save printable image".

3. Choose the desired image resolution

Begin selection by choosing the desired image resolution in dpi from the pull-down list in the Resolution panel.

The entire Region of Interest panel may be ignored for this usage.

4. Use the file browser to specify the file name

Use the browse button to bring up a file browser and navigate to the desired directory in which to save the file. If the file name is not already present (i.e., creation of a new file is desired), enter the desired name of the output file into the browser's text box. After clicking Save in the file browser, the name of the output file will be shown in the Output file name panel.

5. Draw the selection rectangle on the image

After all the parameters have been set, move the cursor (which has changed to a cross-hair) to the desired upper-left corner of the selection and click. A red rectangle will follow the mouse cursor, indicating the boundary of the selection. The actual dimensions of the rectangle and the consequent image are displayed in the Selection size panel while the mouse is being moved. When the rectangle and dimensions are correct, click the mouse again. This will enable the Save button, which has been dimmed prior to this.

6. Save the image and close the annotator

Clicking the Save button will save the image and dismiss the dialog box. Clicking on the Cancel button instead will dismiss the dialog without saving anything.

The selected area of the image will be saved as a JPEG file. The image compression setting used to save the image is generally considered to produce no visible image degradation while providing good compression.

To close the annotator, simply click on the window manager's close button.