In This Chapterrichardson.eng.ua.edu/Former_Courses/AutoCAD_Help/aug_20.pdf · In This Chapter 727 20 Working with Raster Images With AutoCAD® you can add raster images to your vector-based

In This Chapter

727

20

Working with Raster Images

With AutoCAD® you can add raster images to your

vector-based AutoCAD drawings and then view and plot

the resulting file. There are a number of reasons for

combining raster images with vector files, including

scanning documents, faxes, or microfilm drawings;

using aerial and satellite photographs; using digital

photographs; creating effects such as watermarks and

logos; and adding computer-rendered images.

■ Attaching and scaling raster image files

■ Tuning image performance

■ Managing images

■ Clipping images

■ Accessing images from the Internet

■ Controlling image brightness, contrast, and fade

■ Managing image support preferences

728 | Chapter 20 Working with Raster Images

Using Raster Images in Drawings

Raster images consist of a rectangular grid of small squares or dots known as pixels. For example, a photograph of a house is made up of a series of pixels colorized to represent the appearance of a house. A raster image references the pixels in a specific grid.

Raster images, like many other AutoCAD drawing objects, can be copied, moved, or clipped. You can modify an image with grip modes, adjust an image for contrast, clip the image with a rectangle or polygon, or use an image as a cutting edge for a trim.

The image file formats supported by AutoCAD include the most common for-mats used in major technical imaging application areas: computer graphics, document management, engineering, mapping, and geographic information systems (GIS). Images can be bitonal, 8-bit gray, 8-bit color, or 24-bit color.

Several image file formats support images with transparent pixels. When image transparency is set to on, AutoCAD recognizes those transparent pixels and allows graphics in the drawing area to “show through” those pixels. (In bitonal images, background pixels are treated as transparent.) Transparent images can be gray-scale or color.

Although the file extension is listed in the following table, AutoCAD determines the file format from the file contents, not from the file extension.

Attaching and Scaling Raster Images | 729

Attaching and Scaling Raster Images

Images can be referenced and placed in drawing files, but like external refer-ences (xrefs), they are not actually part of the drawing file. The image is linked to the drawing file through a path name. Linked image paths can be changed or removed at any time. By attaching images using linked image paths, or by dragging images using AutoCAD DesignCenter™, you can place images in your drawing and only slightly increase the drawing file size. See “Using AutoCAD DesignCenter to Attach Raster Images” on page 505. You can also access image files from the Internet by specifying a URL. See “Access-ing Raster Images Using the Internet” on page 743.

Supported image file formats

Type Description and versions File extension

BMP Windows and OS/2 bitmap format .bmp, .dib, .rle

CALS-I Mil-R-Raster I .gp4, .mil, .rst, .cg4, .cal

FLIC FLIC Autodesk Animator Animation .flc, .fli

GeoSPOT GeoSPOT (BIL files must be accompanied with HDR and PAL files with correlation data, in the same directory)

.bil

IG4 Image Systems Group 4 .ig4

IGS Image Systems Grayscale .igs

JFIF or JPEG Joint Photographics Expert Group .jpg or .jpeg

PCX Picture PC Paintbrush Picture .pcx

PICT Picture Macintosh Picture .pct

PNG Portable Network Graphic .png

RLC Run-Length Compressed .rlc

TARGA True Vision Raster-Based Data Format .tga

TIFF Tagged Image File Format .tif or .tiff


Once you’ve attached an image, you can reattach it multiple times, treating it as if it were a block. Each insertion has its own clip boundary and its own settings for brightness, contrast, fade, and transparency. You can specify the raster image scale factor when you attach the image so that the scale of the geometry in the image matches the scale of the geometry in the AutoCAD drawing. AutoCAD multiplies the image by the specified scale. The default image scale factor is 1, and the default unit for all images is “Unitless.” The image file can contain resolution information defining the dots per inch (DPI), relating to how the image was scanned.

If an image has resolution information, AutoCAD combines this information with the scale factor and the AutoCAD unit of measurement of the drawing to scale the image in your drawing. For example, if your raster image is a scanned blueprint on which the scale is 1 inch equals 50 feet, or 1:600, and your AutoCAD drawing is set up so that 1 unit represents 1 inch, then in the Image dialog box under Scale, select Specify On-Screen. To scale the image, you clear Specify On-Screen, and then enter 600 in Scale. AutoCAD then attaches the image at a scale that brings the geometry in the image into alignment with the geometry in the drawing.

If no resolution information is defined with the attached image file, AutoCAD calculates the image’s original width to be one unit. After attaching, the image width in AutoCAD units is equal to the scale factor.

To attach and scale an image

1 From the Insert menu, choose Raster Image.

2 In the Select Image File dialog box, select a file name from the list or enter the name of the image file in the File Name box. Then choose Open.

Tuning Image Performance | 731

3 In the Image dialog box, use one of the following methods to specify insertion point, scale, or rotation:

■ Choose Specify On-Screen to use the pointing device to insert the image at the location, scale, or angle you want.

■ Clear Specify On-Screen and enter values under Insertion Point, Scale, or rotation.

To view the unit of measurement for the image, choose Details.

4 Choose OK.

Command line IMAGEATTACH

Related IMAGE displays the Image dialog box, from which you can manage your attached images.

Tuning Image Performance

Manipulating large or many small raster images can make severe demands on system performance. AutoCAD provides a variety of tools that help you work with and manage your image information. For example, if performance slows when you use the Clipboard, you can unload the raster image or turn off the layer containing the image before using the Clipboard.

Changing the Temporary Swap File Location

AutoCAD uses a special temporary image swap file to reduce the amount of RAM occupied by images. The Windows temp directory is the default location of the temporary swap file. You can specify a different directory by adding an entry under Temporary Drawing File Location on the Files tab in the Options dialog box. See OPTIONS in the Command Reference.


Using Tiled Images

Tiled images are small portions (a series of tiles) of large images that load much faster than nontiled images when using AutoCAD. If you edit or change any properties of an image, AutoCAD regenerates only the modified portion, thus improving the regeneration time. TIFF (Tagged Image File Format) is the only tiled format that AutoCAD supports. The TIFF reader supports all image types:

■ Bitonal (1 bit per pixel) ■ Gray scale and indexed color (8 bits per pixel)■ True Color (24 or 32 bits per pixel)

You can save tiled TIFF images with most image scanning tools. The image tiles should be no smaller than 64 × 64 pixels and no larger than 512 × 512 pixels. Additional file readers that support other tiled formats, such as CALS Type II, are available from third-party developers.

Loading and Unloading Images

You can improve performance by unloading images when you do not need them in the current drawing session. Unloaded images are not displayed or plotted; only the image boundary is displayed. Unloading an image does not alter its link. If memory is not sufficient to open multiple attached images in a drawing, AutoCAD automatically unloads images.

In the Image Manager dialog box, you can use Reload to reload an unloaded image or to update a loaded image by reloading the image from the specified directory path. If a drawing is closed after an image is unloaded, AutoCAD does not load the image file when the drawing is next opened; you must reload it.

To unload or reload images

1 From the Insert menu, choose Image Manager.

2 In the Image dialog box, select the image, and then choose Unload or Reload.

or

Select the image name, and then double-click on the status to immediately change the image’s status either from Unload to Reload or from Loaded or Reload to Unload.

The status of the selected image changes.

3 Choose OK.

All instances of the selected attached images are unloaded or reloaded.

Command line IMAGE

Shortcut menu Select an image to load or unload, right-click in the drawing area, and choose Image ➤ Image Manager.


To display specific image instances

1 From the Modify menu, choose Properties.

2 Select the images you don’t want to display.

3 In the Properties window, select Yes or No in the Show Image list.

Shortcut menu Select an image, right-click in the drawing area, and choose Properties.

Detaching Images

You can detach images that are no longer needed in a drawing. When you detach an image, all instances of the image are removed from the drawing, the image definition is purged, and the link to the image is removed. The image file itself is not affected.

To detach an image


2 In the Image dialog box, select the image name.

3 Choose Detach.

The image is no longer linked to the drawing file, and all instances of the image are removed from the drawing.

Command line IMAGE

Shortcut menu Select an image, right-click in the drawing area, and choose Image ➤ Image Manager.

NOTE Erasing an individual instance of an image is not the same as detaching an image. An image must be detached to remove the link from your drawing to the image file.

Highlighting Images

You can turn on or off the highlighting that identifies the selection of a raster image or the image frame by selecting Highlight Raster Image Frame Only on the Display tab in the Options dialog box. You can also set the IMAGEHLT system variable directly. By default, IMAGEHLT is set to 0, to highlight only the raster image frame. Turning off highlighting of the entire image improves performance.


Changing Quality and Speed of Image Display

To increase the display speed of images, you can change image display qual-ity from the default high quality to draft quality. Draft-quality images appear more grainy (depending on the image file type), but they are displayed more quickly than high-quality images.

You can improve the image quality when using True Color (24 or 32 bits per pixel) for raster images by selecting or clearing certain options on the Display tab in the Options dialog box. When AutoCAD displays images at optimum quality, regeneration time increases significantly. To improve performance, decrease the number of colors for the system display setting while working in a drawing. See OPTIONS in the Command Reference.

To change the image display quality

1 From the Modify menu, choose Object ➤ Image ➤ Quality.

2 Enter d (Draft) or h (High).

Images are displayed at the specified quality.

You can increase redrawing speed by hiding images you do not need in the current drawing session. Hidden images are not displayed or plotted; only the drawing boundary is displayed. You can choose to hide an image regard-less of the user coordinate system (UCS) in the current viewport. See “To show or hide an image” on page 734.

Command line IMAGEQUALITY

To show or hide an image

1 From the Tools menu, choose Properties.

2 Select the image to modify.

3 In the Properties window, to show or hide the image, select Yes or No in the Show Image list.

4 To switch the background of the selected image between transparent and opaque, select Yes or No in the Transparency list.


Related PROPERTIES

For more information about using the Properties window, see PROPERTIES in the Command Reference.


Clipping Images

You can increase redrawing speed by clipping the image so that only the parts of the image that you want visible are displayed. You can define the part of an image that you want to display and plot by clipping the image. The clip-ping boundary can be a rectangle or a two-dimensional (2D) polygon with vertices within the boundaries of the image. Each instance of an image can only have one clipped boundary. Multiple instances of the same image can have different boundaries.

NOTE Before you can clip an image, the image boundary must be visible. See “Showing and Hiding Image Boundaries” on page 744.

To clip an image

1 From the Modify menu, choose Clip ➤ Image.

2 Select the image to clip by selecting the image boundary.

3 Enter n (New Boundary).

4 Enter p (Polygonal) or r (Rectangular), and then draw the boundary on the image.

If you are drawing a polygonal boundary, you are prompted to specify con-secutive vertices. To finish drawing a polygon, press ENTER or right-click anywhere in the drawing area.

Command line IMAGECLIP

Shortcut menu Select an image, right-click in the drawing area and choose Image ➤ Clip.

rectangular clipping boundary applied

image after clipping boundary is applied


Changing a Clipping BoundaryYou can change the boundary of a clipped image.

To change the boundary of a clipped image


2 Select the image to clip by selecting the image boundary.

3 Enter n (New Boundary).

4 Enter n (No) or y (Yes) to delete the old boundary.

5 Enter p (Polygonal) or r (Rectangular), and then draw the new boundary on the image.

If you are drawing a polygonal boundary, you are prompted to specify con-secutive vertices. To finish drawing a polygon, press ENTER or right-click anywhere in the drawing area.

You can modify clipped boundaries with grips. See “Editing with Grips” on page 246.


Shortcut menu Select an image, right-click in the drawing area, and choose Image ➤ Clip.

Displaying the Original and the Clipped ImageYou can display a clipped image using the clipping boundary, or you can hide the clipping boundary to display the image with its original boundaries.

To show or hide the clipped portion of an image


2 Choose the clipped image you want to show or hide.

3 In the Properties window, select Yes or No in the Show Image list.


Command line PROPERTIES

Shortcut menu Select a clipped image, right-click in the drawing area, and choose Properties.

Managing Raster Images | 737

Deleting a Clipping BoundaryYou can delete the clipped boundary of an image. When you delete a clipping boundary, the image is displayed with its original boundary.

To delete the boundary of a clipped image


2 Select the clipped image with the boundary you want to delete.

3 Enter d (Delete).

The boundary of the clipped image is deleted, and the original boundary of the image is restored.


Shortcut menu Select an image, right-click in the drawing area, and choose Image ➤ Clip.

Managing Raster Images

You can view image information; attach and detach images; load, unload, and reload images; and change paths to image files using the Image Manager.

To open the Image Manager

■ From the Insert menu, choose Image Manager.

The Image Manager is displayed.

Command line IMAGE


Viewing Image Information

In the Image Manager, you can view image information either as a list or as a tree. To control how the information is displayed in the Image Manager, choose the List View or Tree View button in the upper-left corner. The list view displays the name of each image in the drawing, its loading status, size, date last modified, and search path. The tree view lists the images in a hierarchy that shows their nesting level within xrefs and blocks. The status, size, and other information are not displayed in the tree view.


In either view, you can display information about an image; attach or detach the image; unload or reload the image; and browse for and save a new search path.

Using the List ViewThe list view displays the images attached to the current drawing, but it does not specify the number of instances (see “Viewing Image Information in the Text Window” on page 740). It is the default view. You can sort images by category by clicking the column heading. Change the width of a column by dragging its border to the right or left.

The following information is displayed in the list view:

■ Name of image file■ Status (loaded or unloaded or not found)■ File size■ File type■ Date and time file was last saved■ Name of the saved path

If AutoCAD cannot find an image, its status is listed as Not Found. A Not Found image is displayed as an image boundary in the drawing even if the IMAGEFRAME command is set to off (see “Showing and Hiding Image Bound-aries” on page 744). If the image is unreferenced, no instances are attached for the image. If the image is not loaded, its status is Unloaded. Images with a status of Unloaded or Not Found are not displayed in the drawing.

To display a list of the images attached to the drawing


2 In the Image Manager, choose the List View button.

Command line IMAGE



Using the Tree ViewThe top level of the tree view lists image files in alphabetical order. In most cases an image file is linked directly to the drawing and listed at the top level. However, if an xref or a block contains a linked image, AutoCAD displays additional levels.

To display image names and their nesting levels within xrefs and blocks


2 In the Image Manager dialog box, choose the Tree View button.


Viewing Image File DetailsYou can preview a selected image and view image file details, including

■ Image name■ Saved path■ Active path (where the image is found)■ File creation date■ File size■ File type■ Color■ Color depth■ Image size (pixel width and height, resolution and default size)

To preview an image and view file details


2 In the Image Manager, select an image file.

3 Choose Details.

The file details (image size) and a preview of the image are displayed.

To preview an image that has not been attached


2 In the Select Image File dialog box, select an image file to display a preview.

If a preview of the image is not displayed, choose Show Preview.

3 Choose Open.

4 In the Image dialog box, choose Details.

5 The file details (image size) of the image are displayed.

Viewing Image Information in the Text WindowYou can view image information on the command line. Command line image information includes image name, image path, the number of definitions, and the number of instances of the image attached to the drawing.

To view image information in the text window

1 At the Command prompt, enter -image.

2 Enter ? (List).

3 Press ENTER to list all images.

The AutoCAD text window displays image information as a list.


Changing Image File Paths

When you open a drawing with an attached image, the path of the selected image is displayed at the bottom of the Image Manager under Image Found At. The path displayed is the actual path where AutoCAD found the image file.

If you open a drawing that contains an image that is not in the saved path location, or in any of the defined search paths, the Image Manager displays Not Found in the image list, and the Image Found At box is blank.

To locate the image, AutoCAD first searches the standard AutoCAD search path for the image’s saved path (see “Specifying Search Paths, File Names, and File Locations” on page 74). If AutoCAD cannot locate the image (for example, if you have moved the file to a different directory than the one that was saved with the image), AutoCAD removes relative or absolute path information from the name (for example, \images\tree.tga or c:\my project\images\tree.tga becomes tree.tga) and searches the paths you have defined in the current Project Files Search Path in the Options dialog box. If a project has been defined in the Project Files Search Path, and the PROJECTNAME system variable has been specified (by default, it is Empty), the project name is displayed at the top of the Image Manager. If the draw-ing is not located in the paths specified in the Project Files Search Path, AutoCAD attempts the first search path again. If the saved path doesn’t specify a file extension, all image file extensions are searched.


You can remove the path from the file name or specify a relative path by di-rectly editing the path in the Image Found At box and then choosing Save Path. It may be different from the current Found At path.

For more information about using project files and alternate search paths, see “Creating and Modifying Project Names” on page 476 and “Changing Xref Paths” on page 475. Also see PROJECTNAME in the Command Reference.

Changing the path in the Image Manager does not affect the Project Files Search Path settings.

To change the image path


2 In the Image Manager, select an image whose path you want to change. Then choose Browse.

3 In the Select Image File dialog box, select a new path, and then choose Open.

4 In the Image Manager, choose Save Path to save the new path.

The new path is displayed in the Saved Path column.

5 Choose OK.

Command line IMAGE


Naming Images

Image names are not necessarily the same as image file names. When you attach an image to a drawing, AutoCAD uses the file name without the file extension as the image name. Image names are stored in a symbol table; thus you can change the image name without affecting the name of the file. AutoCAD accepts up to 255 characters for image file names. In addition to letters and numbers, names can have spaces and any special characters not used by Microsoft® Windows® or AutoCAD for other purposes. See “Work-ing with Named Objects” on page 157.

If you attach and place images with the same name but from two different directories, AutoCAD appends numbers to the image names.

Accessing Raster Images Using the Internet | 743

To change an image name


2 In the Image Manager, select the image name.

3 Select the image name again, and then modify the name.

4 Choose OK.

NOTE You can also change the image name by pressing F2 after the current image name is selected and then editing the name.

Accessing Raster Images Using the Internet

Designers and manufactures store images of their designs or products on the Internet. With AutoCAD 2000, you can easily access image files from the Internet. URL image file names are stored in the drawing.

Accessing images from the Internet saves time and provides rapid distribu-tion of designs. For example, an architect who needs to show a client what custom cabinets will look like has the manufacturer create a rendered image of the cabinets, post it to a Web site, and then attach the image to the draw-ing file as a URL; any design changes can be updated immediately. For more information, see chapter 23, “Accessing the Internet.”

To attach and scale an image file from the Internet


2 In the Select Image File dialog box, choose the Search the Web button.

3 In the Browse the Web—Open dialog box, enter the URL for the location of the image file in Look In.

4 Enter the image file name in the File Name box. Then choose Open.

You can also select an image by using the shortcut menu. By right-clicking the image and choosing Properties, you highlight, copy, and paste the com-plete image URL Address into the File Name box.

5 In the Image dialog box, choose OK.

6 If prompted, specify an insertion point and scale factor.


Modifying Images and Image Boundaries

All images have an image boundary. You can select an image by clicking this boundary. Clicking in the middle of an image will not select the image. You cannot use the pointing device to select an image if its boundary is not dis-played. However, with boundaries turned off, you can still select images by layer, by object name, and so on.

When you attach an image to a drawing, the image boundary inherits the cur-rent property settings, including color, layer, linetype, and linetype scale. If the image is a bitonal image, the image color and boundary color are the same.

As with other AutoCAD objects, you can modify images and their boundary properties, including

■ Image layer, boundary color, and linetype■ Display of image boundaries■ Location■ Scale, rotation, width, and height■ Image transparency■ Image brightness, contrast, and fade

You can also modify the quality and speed of the image display, which im-proves performance (see “Changing Quality and Speed of Image Display” on page 734).

Showing and Hiding Image Boundaries

You can hide image boundaries. Hiding the image boundary prevents the boundary from being plotted or displayed. Also, hiding the image boundary prevents you from selecting the image with the pointing device, ensuring that the image cannot accidentally be moved or modified. However, images can still be selected if they are not on a locked layer, for example, if the image is part of a named selection set made with the All option when selecting objects. When image boundaries are hidden, clipped images are still displayed to their specified boundary limits; only the boundary is affected. Showing and hiding image boundaries affects all images attached to your drawing.

image with boundaries off image with boundaries on

Modifying Images and Image Boundaries | 745

To show and hide image boundaries

1 From the Modify menu, choose Object ➤ Image ➤ Frame.

2 To show image boundaries, enter on; to hide image boundaries, enter off.

NOTE When an image frame is turned off, you cannot select images using the Pick or Window options of SELECT.

Changing Image Layer, Boundary Color, and Linetype

You can change the color and linetype of image boundaries and the layer of an image.

To change the image layer, boundary color, or linetype



3 In the Properties window, choose Color.

4 In the Select Color dialog box, select a color and choose OK.

5 In the Properties window, choose Layer or Linetype and make the changes you want by selecting the list in the appropriate field.

The image’s properties are modified.

See “Using the Properties Window” on page 260.



Moving ImagesYou can move images with grips. To move the image to a precise location, use the Properties window. For information about using grips, see “Editing with Grips” on page 246.

To move an image


2 Select the image to move.


3 In the Properties window, to move the image to a precise location, enter coor-dinate values for X, Y, or Z.

4 Press ENTER.

The image moves to the new location. See “Using the Properties Window” on page 260.



Changing Image Scale, Rotation, Width, and Height

As with any AutoCAD drawing object, you can change image scale, rotation, width, and height.

You can modify images with grips. See “Editing with Grips” on page 246.

To change image parameters



3 In the Properties window, to change image scale, rotation, and width/height, enter a value in the appropriate field. Then press ENTER.

Changing the image width and height maintains the aspect ratio of the image. The image rotates around its insertion point.




Modifying Bitonal Image Color and TransparencyBitonal raster images are images consisting only of a foreground color and a background color. When you attach a bitonal image, the foreground pixels in the image inherit the current settings for color. In addition to the modifi-cations you make to any attached image, you can modify bitonal images by changing the foreground color and by turning on and off the transparency of the background.

NOTE Bitonal images and their boundaries are always the same color.

Modifying Images and Image Boundaries | 747

To change the color and transparency of a bitonal image



3 In the Properties window, to change image color, choose Color.

4 In the Select Color dialog box, specify a color and choose OK.

5 To change the background of the selected image to transparent, or to change the background image from transparent to opaque, select Yes or No in the Transparency list.

To change only the transparency of a bitonal image

1 From the Modify menu, choose Object ➤ Image ➤ Transparency.


To change the background of the selected image to transparent, enter on. Enter off to change the background to opaque.

Command line TRANSPARENCY

Shortcut menu Select an image, right-click in the drawing area, and choose Transparency.

image of a watch face with transparency

conceptual rendering of the watch case constructed and rendered in 3D Studio

result after importing the face layout into AutoCAD, making it transparent, and then placing it over the rendering


Adjusting Image Brightness, Contrast, and Fade

You can adjust brightness, contrast, and fade for the display of an image as well as for plotted output without affecting the original raster image file and without affecting other instances of the image in the drawing. Adjust bright-ness to darken or lighten an image. Adjust contrast to make poor-quality images easier to read. Adjust fade to make drawing geometry easier to see over images and to create a watermark effect in your plotted output.

Bitonal images cannot be adjusted for brightness, contrast, or fade. Images fade to the current screen background when displayed, and they fade to white when plotted.

To adjust brightness, contrast, and fade of an image

1 From the Modify menu, choose Object ➤ Image ➤ Adjust.


3 In the Image Adjust dialog box, to adjust brightness, contrast, and fade, use the appropriate slider or enter a value.

The default value for both brightness and contrast is 50. You can adjust to a maximum brightness of 100 or to a minimum of 0. The default fade value is 0. You can adjust to a maximum fade of 100.

4 Choose OK.

Command line IMAGEADJUST

Shortcut menu Select an image, right-click in the drawing area, and choose Image ➤ Adjust.

Related To change the brightness, contrast, or fade values of an image, use PROPERTIES.

Documents

In This Chapterrichardson.eng.ua.edu/Former_Courses/AutoCAD_Help/aug_20.pdf · In This Chapter 727 20 Working with Raster Images With AutoCAD® you can add raster images to your vector-based