Lesson 1 Enhancing raster images

Brief description: During this lesson you will learn ways of enhancing raster images. Using examples, you'll find out how to remove speckles from a raster image, separate an image by size, apply the Smoothing filter, deskew a scanned image and apply four-point correction.

See section Enhancing Scanned Images of the Quick Start guide for detailed information on enhancing raster images.

Speckle Remover

Create a new AutoCAD drawing.

Using the Open command from the rFile menu, load the Sample1.tif file from the Lesson_1 folder.

To enhance the raster image let's apply the Speckle Remover filter, then four-point correction to eliminate the distortions.

To remove speckles choose Speckle Remover from the Filters menu.

Estimate the max speckle size on the screen using the measure tool . To help select a speckle, use Zoom and Pan (see the commands of the View menu). Click Apply.

Fig.1-1 The original document	Fig. 1-2 After removing speckles

Four point correction

To eliminate distortions choose 4 point Correction from the Image menu. Specify the frame size in the Width (265 mm) and Height (180 mm) fields. Press the Measure Frame button and specify the four corners of the document frame one by one. Press OK.

Fig. 1-3 Specifying 4 frame corners	Fig. 1-4 After 4-point correction

• Save the corrected image using Save or Save As from the rFile menu.
• As you have applied all required operations to this image, you can
• Erase the saved image. To do this, you need to select it by clicking on the frame with the cursor, and then press Erase.
• Unload the image using AutoCAD Image Manager. To open Image Manager, choose Image Manager from the Insert menu. Select the image from the list, and then press Detach.
• Close the AutoCAD document (with or without saving it); to save the document choose Save or Save As from the rFile menu.

Separating by size

When applying the Speckle Remover filter, you can accidentally remove small important objects, whose size is close to the speckle size. If this happens, an alternative is to use the operation of separating raster particles by size. The principle of this operation is similar to speckle removing, except speckles are not removed but transferred to a new raster image.

Create a new AutoCAD drawing (if you have closed the previous one).

Choose Open from the File menu. Open the Sample2.tif file from the Lesson_1 folder.

To separate the speckles from the raster image choose Separation by Size from the Images menu. Estimate the max speckle size on the creen using the measure tool . Choose a color and (if needed) a name for the new image that you want to transfer the raster speckles to. Click Apply.

Fig.1-5 Original document	Fig.1-6 After separation

In figure 1-6 one of the centerline fragments that were incorrectly transferred to the speckle layer, is marked with an arrow. Perform the following actions to bring the fragments back to the original image:

Select the fragments that were incorrectly transferred to the speckle layer.

• On the Raster Select toolbar press the Add    button to add data to the selection.

In this example, it is best to select the raster fragments using the tool - Select Raster Floodfill  - press the corresponding button on the Raster Select toolbar. In the Select Image dialog select the checkbox for the image containing the speckles. Press OK.

Use the mouse cursor to specify the particles to be transferred back to the original layer.

Choose Merge from the rEdit menu. The selected particles will be merged with the original layer.

Deskewing

To deskew the image with automatic definition of the rotation angle, choose Deskew from the rImage menu, and then select Auto.

Fig.1-7 Before deskewing	Fig.1-8 After deskewing

• Save the raster image and close it as described above.

Smoothing

Create a new AutoCAD drawing.

Choose Open from the File menu. Open the Sample3.tif file from the Lesson_1 folder.

• Choose the Smoothing filter from the Filters menu.
• Use the sliders - Medianing & Threshold - to achieve the best results in the preview window.

INFORMATION: You can change the position of the preview window using the Preview Area button located on the WiseImage toolbar.

Fig.1-9 Before applying Smoothing	Fig.1-10 After applying Smoothing

• Save and close the raster image as described above

 [ welcome ]   [ hybrid graphics ]   [ quick start ]   [ tutorial ]   [ reference ]   [ about ] 
 
 [ Welcome ]  [ WiseImage for Windows ]   [ WiseImage for AutoCAD ]