Raster Editing

Brief description: This section highlights some of the different methods of editing selected raster data, and also the commands designed for editing raster images.

Editing data, selected with object selection methods

Let us consider different methods of editing raster data, selected with the object selection methods:
You can view and edit the properties and geometry of selected objects using the AutoCAD Property window.

Selected raster object	The raster object properties in the Properties window

• You can change the geometry of raster objects, and also the location of selected objects on screen using “grips”.

Editing Raster Images

The commands from the rImage menu are designed for editing raster images.

The commands from the rImage menu modify the raster image contents – for example, resolution, real size, size in pixels, point’s positions. You should understand the difference between the image editing commands of AutoCAD, and those of the rImage menu. Unlike the commands of the rImage menu, the AutoCAD commands do not change the raster image contents. For example:

• The AutoCAD Scale command of the AutoCAD Modify menu only changes the scale of the raster insertion; the raster image contents (resolution, number of points and location) are not changed.
• Using the Scale field of the Resample dialog box, you can modify the raster image contents – resolution and/or the number of points the image is composed of.        

Change Image Size

Choose Change Size from the rImage menu.

Using the Change Size dialog box you can:

• Change the image size to the desired format:
  Select the desired format from the Standard Paper Size list. Set the image orientation – Portrait or Landscape.
• Change the image size to the closest standard format:
  Press Find Closest.
• Add (or cut) image margins:

You can also align the image position relative to its margins:

• Using one of the nine buttons of the Alignment/Margins field.
• Entering the margin values in the Alignment/Margins section with the Fixed Size checkbox set to on.        

Resample

Using the Resample dialog from the rImage menu you can:

• Proportionally change the image size with a fixed resolution.
  • Choose the measurement units from the list (you can choose pixels as measurement units).
  • Enter the new values in the Width and Height fields.
  • The Fixed size in pixels checkbox is off.
• Change the image size according to the specified Scale value with fixed resolution. 
  • Enter the new scale value in the corresponding field.
  • The Fixed size in pixels checkbox is off. 
• Change the image resolution, with fixed size. 
  • Enter the new resolution value in the corresponding field. 
  • The Fixed size in pixels checkbox is off. 
• Change the image resolution (size); the number of pixels is fixed. 
  • Turn on the Fixed size in pixels checkbox. 
  • Enter the new resolution (size, scale) value.

Cropping Images

Cropping commands are located in the Crop submenu of the rImage menu.

You can:

• Crop blank margins of the raster image.
• Crop the raster image by its frame.
• Crop the raster image by a rectangle specified on screen.
• Crop the raster image by clip.       

Rotate and mirror

These commands located in the rImage menu, allow you to rotate an image by 90°, 180°, 270°, or by an arbitrary angle, and also mirror an image about the X or Y-axis.