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Working with Raster Images

You can easily import scanned images, digital photographs, and other image files into your drawings. You can use these images to insert a logo, show a photo or artist’s rendering of your model, and for many other uses. Although raster (bitmap) images are generally much larger files than vector drawings, you can easily zoom and pan throughout your drawing. You can usually plot these raster images as well. Table 27-2 shows the raster formats that AutoCAD 2005 supports.

You cannot insert raster images into AutoCAD LT. However, you can open an AutoCAD drawing that contains images and view the image. You can also use the IMAGE command to obtain information about the image. You can copy, move, and resize the image.

Table 27-2: Raster Formats Supported by AutoCAD 2005

File Type	File Extension	Comments
BMP	.bmp, .dib, .rle	Windows and OS/2 bitmap
CALS-1	.gp4, .mil, .rst, .cg4, .cal	Mil-R-Raster 1
GIF	.gif	CompuServe Graphics Exchange Format
GeoSPOT	.bil	GeoSPOT (used in GIS applications); HDR and PAL
		files with correlation data must be in the same
		folder
JFIF or JPEG	.jpg, .jpeg	Joint Photographic Expert Group
FLIC	.flc, .fli	Autodesk Animator FLIC
IG4	.ig4	Image Systems Group 4
IGS	.igs	Image Systems Grayscale
PCX	.pcx	Paintbrush
PICT	.pct	Macintosh picture
PNG	.png	Portable Network Graphic
RLC	.rlc	Run-Length Compressed
TARGA	.tga	True Vision Raster-Based Data Format
TIF	.tif, .tiff	Tagged Image File Format

Inserting images

It’s easy to insert an image into your AutoCAD drawing. After you insert the image, you can manipulate it in a number of ways. To insert an image, choose Insert Raster Image to open the Select Image File dialog box.

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Locate the image you want to insert and choose Open. The Image dialog box (shown in Figure 27-5) opens; this dialog box lets you specify how to insert the image. You can specify the insertion point, scale, and rotation in the dialog box or on-screen. This dialog box is very similar to the Insert dialog box that you use when inserting drawings and blocks.

New	You can now specify a relative path (instead of the full path) for an image. A relative path
Feature	stores only the relationship between the drawing and the image. If you put the image in the
	same folder as the drawing, only the drawing name is stored. Using a relative path and plac-
	ing the image in the same folder as the drawing is ideal when you need to share drawings
	with people who don’t have the same folder structure as you.

Figure 27-5: The Image dialog box.

Click Details to open the bottom of the dialog box. Here the dialog box lists the resolution (number of pixels) per drawing unit and the size in pixels, as well as the size in drawing units. The Current AutoCAD Unit is based on the specification in the Units dialog box. (See Chapter 5 for more information.) This information is helpful in deciding how to scale an image.

Note Raster images usually don’t scale up very well. If you enlarge them too much, the dots get too far apart, and the image looks grainy. However, the higher the resolution, the better the image will look when enlarged.

Click OK to insert the image.

You can also use the DesignCenter to insert raster images, as described in Chapter 26.

The Express Tools contain a command, IMAGEEDIT (choose Express File Tools Edit Image), that opens a selected image in a specified image-editing application.

Managing images

As with xrefs, you may need a way to keep track of your images, especially if you insert many of them. Choose Insert Image Manager to open the Image Manager (as shown in Figure 27-6), which enables you to manage the images in your drawing. You can insert images from this dialog box as well.

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Figure 27-6: The Image Manager.

You can use the List view and Tree view buttons at the top of the dialog box to view your images in a flat list or a hierarchical (tree) format. Here are the other options:

Attach inserts an image, opening the Image dialog box (refer to Figure 27-5).

Detach erases the image from your drawing and deletes all references to it in the drawing database.

Reload redisplays an image after you’ve unloaded it.

Unload removes the display of the image but retains the reference to it. Later, you can reload the image to redisplay it.

Details provides you with a preview, as well as information about the image, its path, and its size.

The Image Found At box shows you the location of the image. If you didn’t save a path when attaching the image, you can do so by clicking Save Path. You can also find an image whose Status shows Not Found by choosing Browse. This would happen if you moved the image after attaching it.

Tip	You can attach rendered images that you’ve saved as TIF, TGA, or BMP files. A great way to do
	this is to create a floating viewport in paper space for the rendered image, letting your clients
	see not only the regular drawing but the rendered result on one sheet of paper. (Figure
	25-24 in Chapter 25 was created this way.) Remember that you can plot shaded and ren-
	dered images. See Chapter 17 for details.

Clipping images

A powerful feature of AutoCAD lets you clip images just as you clip external references. Large images can slow down your drawing display. You may also simply find it distracting to see parts of an image that you don’t need for your work. For example, if you attach an aerial photograph of a city block but want only one house, being able to clip around the house and not display the rest of the image is a great advantage.

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To clip an image, follow these steps:

1.Insert an image.

2.Choose Modify Clip Image.

3.At the Select image to clip: prompt, select the image. Pick the image at its border.

4.At the prompt, press Enter to accept the default of creating a new clipping boundary.

5.At the Enter clipping type [Polygonal/Rectangular] <Rectangular>: prompt, press Enter to create a rectangular clip or right-click and choose Polygonal to create a multisided boundary.

•For a rectangular boundary, pick a first point and the opposite corner to create the boundary.

•For a polygonal boundary, specify the first point and then use the Specify next point or [Undo]: prompt to pick points until you’ve completed the boundary. You can use the Undo option to undo the last pick or the Close option (which appears after you pick three points) to close the final boundary. AutoCAD creates a rubber-band boundary as you pick points so you can see the result. Press Enter when you’re done.

	At the Enter image clipping option [ON/OFF/Delete/New boundary] <New>: prompt,
	you can also use the following options:
	Choose ON to turn on a boundary that you previously turned off.
	Choose OFF to turn off a boundary and redisplay the entire image.
	Choose Delete to delete the clipping boundary.
Note	Images are 2D objects. The clipping boundary must be parallel to the plane of the image. For
	information on placing images on 3D objects, see the “Mapping” sidebar in Chapter 25.

Controlling image display

You can control several aspects of image display using the commands detailed in this section. Control the image display to adjust the properties that control how the image looks.

Image display

The IMAGEADJUST command lets you change the brightness, contrast and fade of an image. Choose Modify Object Image Adjust to start the IMAGEADJUST command and open the Image Adjust dialog box, shown in Figure 27-7.

This dialog box enables you to dynamically change the brightness, contrast, and fade of the image, using the slider bars or text boxes. You immediately see the results in the preview box. Choose Reset to return the image to its original status.

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Figure 27-7: The Image Adjust dialog box.

Image quality

Choose Modify Object Image Quality to start the IMAGEQUALITY command. AutoCAD displays the Enter image quality setting [High/Draft] <High>: prompt. Choose either High or Draft. This command affects the display of all the images in a drawing. Use it when a high-quality image slows down performance. A regen is not necessary after you change this setting. Plotting is always done at high quality.

Image transparency

If the image format you’re using supports transparent pixels, you can use the TRANSPARENCY command to create a transparent background for your image. This works for bi-tonal or grayscale images. (Bi-tonal images have only a foreground and a background color.) By default, transparency is off.

To turn transparency on, choose Modify Object Image Transparency and select the image(s) you want to change. At the Enter transparency mode [ON/OFF] <OFF>: prompt, type on and do a regen. Other objects in your drawing will now be visible through the background of your image.

	Image frame
	The IMAGEFRAME command turns off the frame that surrounds all images in a drawing.
	Choose Modify Object Image Frame. Turning off the frame often improves the way the
	image looks. However, you select an image by clicking its frame. Therefore, an Off setting
	means you cannot select the image, except when using commands specific to images, such
	as TRANSPARENCY, IMAGEADJUST, and IMAGECLIP.
Tip	Don’t turn the frame off until you’ve finished editing the image. You can also select raster
	images using Quick Select. Because raster images are considered to be on the layer that is
	active when they’re inserted, you can use Quick Select to select them by layer.

When an image has a border, the border displays the properties of the layer that was current when the image was inserted. You can use the IMAGEFRAME in AutoCAD LT to turn the frame on and off.

848 Part V Organizing and Managing Drawings

Draw order

The DRAWORDER command (Tools Draw Order) changes the display order of objects, including raster and OLE objects. (OLE is discussed later in this chapter.) This command is very helpful when working with raster and OLE objects, where you may or may not want to hide the other objects in your drawing. You can move an object to the top or bottom or change its order in relation to another object — above or below it. To change an object’s display order, choose Tools Display Order and choose one of the submenu options. At the prompt, select objects. Draw order settings are saved with the drawing.

New

Feature

On the

CD-ROM

You now have more DRAWORDER options. You can bring to front, send to back, bring above object, or send under object. The new TEXTTOFRONT command controls the order of both text and dimensions.

The drawing used in the following Step-by-Step exercise on working with raster images, ab27-b.dwg, and the images ab27-b.tif and ab27-b1.bmp, are in the Drawings folder on the CD-ROM. This exercise works with AutoCAD only.

STEP-BY-STEP: Working with Raster Images

1.Open ab27-b.dwg from the CD-ROM.

2.Save the file as ab27-03.dwg in your AutoCAD Bible folder.

3.Choose View 3D Views Top.

4.Choose Insert Raster Image.

5.In the Select Image File dialog box, choose ab27-b.tif from the CD-ROM. Click Open. Click Details. Notice that the image is 1×0.61 units. Compared to the house, it is tiny.

6.In the Image dialog box, uncheck Specify on-screen for the Scale factor and change the scale factor to 5. Click OK.

7.At the Specify insertion point <0,0>: prompt, pick any point on the left side of the screen. The image is still tiny, but that’s okay. Choose Zoom Window from the Zoom flyout of the Standard toolbar to zoom closely into the image.

8.Choose Modify Object Image Adjust. At the Select image(s): prompt, select the image by picking its frame. Press Enter. In the Image Adjust dialog box, change the Contrast to 60 and the Brightness to 40. Choose OK.

9.Choose Modify Clip Image. At the Select image to clip: prompt, select the image again, which is shown in Figure 27-8. Follow the prompts:

Enter image clipping option [ON/OFF/Delete/New boundary] <New>: Enter clipping type [Polygonal/Rectangular] <Rectangular>: Specify first corner point: If OSNAP is on, turn it off. Pick 1 in Figure 27-8.

Specify opposite corner point: Pick 2.

10.Use Zoom Realtime to zoom out so that you have room to insert another image. Choose Insert Raster Image and attach ab27-b1.bmp (located on the CD-ROM) with a scale factor of 5. Insert it below the first image.

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2

1

Figure 27-8: Clipping the raster image.

11.Click the Layout1 tab to enter paper space, which has three floating viewports. Click PAPER to enter model space. Click the bottom-left viewport. Choose View 3D Views Top. You should now see the images as a small dot to the left of the house. Use Zoom Window to zoom into the rendered table. Your drawing should now look like Figure 27-9.

1

Figure 27-9: The drawing with a rendered view in one viewport.

12.Click the right viewport. If necessary, pan the house to the right until you can see the two images you attached. Move the Cottonmill Houses image to 1 in Figure 27-9. Scale it, using a base point at its lower-left corner and a scale factor of 25. Move it until it fits nicely in the upper-right corner of the floor plan. Pan again to center the house in the viewport. (If it disappears, do a Zoom Extents.)

13.Choose Modify Object Image Frame. Right-click and choose Off. AutoCAD removes the frames from the two images.

14.Save your drawing.