Displaying and Modifying Rendered Images

Rendered images that you have saved to disk can be recalled for viewing and modification in MicroStation, via the Display Image dialog box (Utilities > Image > Display).

When you view your saved images via the Display Image dialog box (Utilities > Image > Display), you see the image without MicroStation´s view Gamma Correction. Any gamma correction that you specified at the time of saving will be part of the saved image, but the view gamma correction is ignored. Gamma correction that has been set at the system level, however, will have an effect on the displayed image.

General Procedure — To view a saved rendered image

1. From the Utilities menu's Image submenu, choose Display.
   The Display Image dialog box opens.


2. From the List Files of Type option menu, choose the format of the image file to display.


3. In the Files list box, select the image file to display.


4. Click the OK button.
   The Display Image dialog box closes and a display window opens in which the selected image is displayed. The window's title bar indicates the filename, pixel dimensions and color depth.

   Image display window



5. (Optional) Perform image modifications by using items in the display window's Edit and Image menus:

   File menu	Open — Open an existing image.
   	Save As — Save an image with a new name.
   	Save — Save an image with its current name.
   Edit menu	Cut/Copy/Paste — Copy or move a portion of the image. See To move or copy a portion of the image.
   	Size — Resize the image by specifying a new pixel count. See To resize the image.
   	Crop — Trim the image to a specified rectangle. See To trim (crop) the image.
   	Rotate > — Rotate the image 90 CW, 90 CCW or 180 degrees. See To rotate the image.
   	Mirror > — Mirror the image along the horizontal or vertical axis. See To mirror the image.
   Image menu	Equalize — Perform a histogram equalization on the image color palette.
   	Gamma Correction — Lighten or darken the mid-range colors of the image.
   	Tint — Tint the image.
   	Negate — Invert the image to appear like a film negative.
   	Blur — Smooth jagged edges through pixel averaging.
   Color Mode — Change the color depth of the image.



6. (Optional) Replace the image file on disk with the modified image, or save the modified image to a new file on disk in the same or different format. See Saving image modifications.
   or
   (Optional) If the result of the modifications is undesirable, just reopen the image using Open from the display window's File menu or simply close the display window without saving.

To move or copy a portion of the image

1. Locate the pointer on one corner of the rectangular area to move or copy, and then press and hold down the Data button.


2. Drag the resulting selection rectangle to the opposite corner of the desired area, and then release the Data button.
   A dynamic rectangle indicates the area to be cut or copied.


3. From the display window's Edit menu, choose Copy.
   or
   From the display window's Edit menu, choose Cut to replace the selected area with the background color.


4. From the display window's Edit menu, choose Paste.
   The selected area appears in the upper left corner of window.


5. Relocate the portion to its new location by pressing and holding down the Data button and dragging the image to its new location.


6. Once the portion is positioned where you want it, click once inside the selection.



Should you decide to cancel the pasting operation while the pasted selection rectangle is active, click once anywhere outside the selection rectangle. This results in the disappearance of the pasted image. It does not, however, reverse the cut operation.

To resize the image

1. From the display window's Edit menu, choose Size.
   The Size Image dialog box opens.
   There are two fields: X Resolution and Y Resolution. Each can be specified directly or, if the two fields are locked, a change to one field results in a change in the opposite file, thus maintaining the image's aspect ratio.


2. Key in the desired sizes.


3. Click the OK button.



You cannot specify a size larger than the working size of the MicroStation application window. If a value larger than this is entered, the image is scaled to fit in the application window.

To trim (crop) the image

1. Locate the pointer on one corner of the rectangular area to which you wish to trim the image, and then press and hold down the Data button.


2. Drag the resulting selection rectangle to the opposite corner of the desired area, and then release the Data button.
   A dynamic rectangle indicates the area that will remain at the conclusion of the crop operation.


3. From the display window's Edit menu, choose Crop.

To rotate the image

1. In the display window, choose the appropriate item from the Edit menu's Rotate submenu:

Rotate >	Used to:
90 CW	Rotate the image 90° clockwise.
90 CCW	Rotate the image 90° counterclockwise.
180	Rotate the image 180°.

To mirror the image

1. In the display window, choose the appropriate item from the Edit menu's Mirror submenu:

Mirror >	Used to:
Horizontal	Mirror the image about the horizontal (x-) axis.
Vertical	Mirror the image about the vertical (y-) axis.

Equalize

The Equalize function is used to color-correct a washed out or overly dark image. This is done by finding the highest and lowest values for the red, green and blue components of each color. Once these values are identified, an averaging operation is performed to push the high and low values to white and black respectfully. This results in a wider separation of dark to light areas in the image.

To equalize the image

1. From the Image menu, choose Equalize.

Gamma Correction

Similar in operation to the Picture control on a television, the Gamma Correction function brightens or darkens a large portion of what is known as the middle colors of an image. This avoids changing a true black or white value to a gray value.

In general, Gamma Correction helps improve a dark image so that subtle details can be seen.

Two typical methods for working with Gamma Correction are:

1. Save the image at the default gamma value of 1.0, to avoid data loss, and then enable gamma correction at display time.

2. Save the image with the gamma set for the brightest media, say 1.8 for display, then adjust the value for printing.

You can set the gamma value for an image when you create a saved image. At a system level, you can set the gamma value for your display by selecting Workspace > Preferences > View Options and setting the value for Gamma Correction.

To gamma correct the image

1. From the Image menu, choose Gamma Correction.
   The Gamma Correction dialog box opens.


2. Adjust the slider towards the right for a lighter image or towards the left for a darker image. The Gamma Correction field will update to show the current numeric value.
   or
   Directly enter the value in the Gamma Correction field. An acceptable value is in the range 0-2, with 1.00 representing no correction. Decreasing the value results in a darkening of the image while increasing the value results in a lighter image.


3. Click the Apply button to process the image with the value entered.
   or
   Click the Preview button to see the change without modifying the image in memory.

Tint

The Tint function modifies the RGB value of each pixel in the image.

For instance, to “tint” an image with a touch of yellow, you would adjust the blue color to a lower value. This subtracts blue and reveals its complement — yellow. Setting red, green or blue to zero causes that color to be removed from the image. This also causes the complement to that primary color to dominate the image.

To tint the image

1. From the Image menu, choose Tint.
   The Tint Image dialog box opens.


2. Adjust the RGB values either by adjusting the sliders or directly entering a value in the appropriate field.


3. Click the Apply button to process the image.
   or
   Click the Preview button to see the change (in memory) without modifying the image.

Negate

The Negate function converts an image into its negative or color complement. This function is especially useful for enhancing dark grayscale images where details are easily lost in the black background.

To invert or negate the image

1. From the Image menu, choose Negate.

Blur

The Blur function minimizes jagged edges by creating a smooth transition between adjacent pixels.

To blur the image

1. From the Image menu, choose Blur.

Color Mode

All images are organized by their resolution and their color depth. Color depth refers to the number of bits assigned to each pixel in the image. The more bits, the larger the number of colors that can be represented. MicroStation can be used to display images with anywhere from 1 bit of color (black-and-white) to 24 bits of color (also known as “true” or RGB color).

The Color Mode function is used to adjust an image's color depth either up or down. This means you can take an image that

contains 24 bits of color (representing 16.7 million possible colors) and reduce it to black-and-white, grayscale (256 shades of gray), 16 colors or 256 colors.

In response to a request to reduce the color depth — for example, from 256 colors to 16 — the image is dithered. This is a method by which adjacent pixels are modified in color to approximate the previous value of the center pixel. This is similar in function to how magazines produce color on the printed page.

To change the color depth of the image

1. In the display window, choose the appropriate item from the Image menu's Color Mode submenu:

   Color Mode >	Used to:
   RGB	Change the color depth to 24 bits (256 red, 256 green, 256 blue) for 16.7 M possible colors
   16 Colors	Change the number of colors to 16 (4-bit color depth)
   256 Colors	Change the number of colors to 256 (8-bit color depth)
   Grey Scale	Process all colors to the closest grayscale value (256 shades of gray)
   Monochrome	Process all colors (or grays) to 1-bit or black-and-white (using extreme dithering)

When you save an image to a format that does not support the current image's color depth (a common occurrence), a Color Mode operation can be performed to adjust the color depth prior to the save image operation, or you will be prompted to accept a supported color mode that will not result in loss of detail.

Saving image modifications

You can save a modified image either by replacing the original image file on disk or creating a new image file. In the latter case, the new file need not have the same format.

To save changes to the image file

1. From the display window's File menu, choose Save.

To save a modified image to a new image file with the same or different format

1. From the display window's File menu, choose Save As.
   The Save Image As dialog box opens.


2. From the Format Type option menu, choose the image file format and, from the Compression option menu, the compression level.


3. In the Files field, key in the filename.


4. Click the OK button.



You can save an image file in a different format using Save As even if you have not modified the image. The same result can be accomplished by using the Raster File Conversion utility (Utilities menu > Image > Convert).