Scaling a Raster Image

The raster1.jpg file was scanned as a grayscale image at 100 dpi. This shows that you can get a reasonable amount of detail at a fairly low scan resolution.

Now suppose that you want to trace over this image to start an AutoCAD drawing. The first thing that you should do is scale the image to the appropriate size. You can scale an image file to full size. Try the following steps to see how you can begin the process:

1. Choose Zoom Extents from the Zoom flyout on the Navigation bar, or type Z↵E↵. You may also want to pan the view or move the Xref palette to get a clear view of the drawing.
2. Turn on Polar Tracking or Ortho mode, and then click Scale on the Home tab's Modify panel.
3. Click the edge of the raster image to select it.
4. Press ↵ to finish your selection.
5. At the Specify base point: prompt, click the X in the lower‐left corner of the image.
6. At the Specify scale factor or [Copy/Reference]: prompt, enter R↵ to use the Reference option.
7. At the Specify reference length <0′ ‐1″>: prompt, type @↵. This tells AutoCAD that you want to use the last point selected as one end of the reference length. After you enter the @ symbol, you'll see a rubber‐banding line emanating from the X.
8. At the Specify second point: prompt, click the X at the lower‐right corner of the image.
9. At the Specify new length or [Points] <0′ ‐1″ >: prompt, enter 44′↵. Metric users should enter 1341↵. The image enlarges. Remember that this reference line is 44′, or 1341 cm, in length.

The image is now scaled properly for the plan it portrays. You can proceed to trace over the image. You can also place the image on its own layer and turn it off from time to time to check your trace work. Even if you don't trace the scanned floor plan line for line, you can read the dimensions of the plan from your computer monitor instead of having to go back and forth between measuring the paper image and drawing the plan on the computer.

Controlling Object Visibility and Overlap with Raster Images

With the introduction of raster image support, AutoCAD inherited a problem that's fairly common to programs that use such images: Raster images obscure other objects that were placed previously. The image you imported in the previous exercise, for example, obscures the line you drew when you first opened the file. In most cases, this overlap isn't a problem. However, in some situations, you'll want AutoCAD vector objects to overlap an imported raster image. An example is a civil‐engineering drawing showing an AutoCAD drawing of a new road superimposed over an aerial view of the location for the road.

Paint and page‐layout programs usually offer a “to front/to back” tool to control the overlap of objects and images. AutoCAD offers the Draworder command. Here's how it works:

1. Click Zoom Extents on the Navigation bar or type Z↵E↵ to get an overall view of the image.
2. Choose the Bring Above Objects tool from the Draworder flyout on the Home tab's expanded Modify panel.

   

3. At the Select objects: prompt, select the horizontal line that you drew when you first opened the file.
4. If there are other objects in the drawing that you want to “bring above objects,” you can select them as well. Press ↵ to finish your selection.
5. At the Select reference objects: prompt, click the edge of the raster image of the utility room and then press ↵.

The drawing regenerates, and the entire line appears, no longer obscured by the raster image.

The Draworder tool that you just used has nine options in the Draworder flyout on the Home tab's Modify panel:

• Bring To Front   Places an object or a set of objects at the top of the draw order for the entire drawing. The effect is that the objects are completely visible.

• Send To Back   Places an object or a set of objects at the bottom of the draw order for the entire drawing. The effect is that other objects in the drawing may obscure those objects.

• Bring Above Objects   Places an object or a set of objects above another object in the draw order. This has the effect of making the first set of objects appear above the second selected object.

• Send Under Objects   Places an object or a set of objects below another object in the draw order. This has the effect of making the first set of objects appear underneath the second selected object.

• Bring Text To Front   Automatically places all text in a drawing in front of all objects.

• Bring Dimensions To Front   Automatically places all dimensions in a drawing in front of all objects.

• Bring Leaders To Front   Automatically places all dimension leaders in a drawing in front of all objects.

• Bring All Annotations To Front   Automatically places all annotation objects in a drawing, including dimensions, in front of all objects.

• Send Hatches To Back   Automatically sends all hatch patterns in a drawing behind other objects.

You can also use the DR keyboard shortcut to issue the Draworder command. If you do this, you see these prompts:

Select objects:
Enter object ordering option [Above objects/Under objects/Front/Back]<Back>:

After selecting an object or set of objects at the Select Objects: prompt, press ↵. You must then select the option by typing the capitalized letter of the option.

Although this section discussed the Draworder tools in relation to raster images, they can also be invaluable in controlling visibility of line work in conjunction with hatch patterns and solid fills. See Chapter 7 for a detailed discussion of the Draworder tools and hatch patterns.

Adjusting Brightness, Contrast, and Fade

AutoCAD offers a tool that enables you to adjust the brightness, contrast, and fade of a raster image. Try making some adjustments to the raster image of the utility room in the following exercise:

1. Click the edge of the raster image. The Image tab appears in the Ribbon (see Figure 13.4).

   

2. In the Adjust panel of the Image tab, click and drag the Fade slider to the right so that it's near the middle of the slider scale, or enter 50 in the Fade box to the right of the slider. The sample image fades to the AutoCAD background color as you move the slider.
3. Press the Esc key to unselect the raster image. The Image tab closes.
4. Save the file as Rasterimport.dwg.

You can adjust the brightness and contrast by using the other two sliders in the Adjust panel of the Image tab.

By using the Image tab in conjunction with image clipping, you can create special effects. Figure 13.5 shows an aerial view of downtown San Francisco with labels. This view consists of two copies of the same raster image. One copy serves as a background, which was lightened using the method demonstrated in the previous exercise. The second copy is the darker area of the image with a roughly triangular clip boundary applied. You might use this technique to bring focus to a particular area of a drawing that you're preparing for a presentation.

If the draw order of objects is incorrect after you open a file or perform a Pan or Zoom, issue a Regen to recover the correct draw‐order view.

In addition to the tools in the Adjust panel, there are several tools in the Image tab that can be used to modify raster images. Table 13.1 gives you a rundown of their function.

Clipping a Raster Image

In Chapter 7, you saw how you could clip an external reference object so that only a portion of it appears in the drawing. You can clip imported raster images in the same way. Just as with Xrefs, you can create a closed outline of the area that you want to clip, or you can specify a simple rectangular area.

In the following exercise, you'll try the Clip command to control the display of the raster image:

1. Select the Clip tool from the Insert tab's Reference panel, or type Clip↵.

   

2. At the Select object to clip: prompt, click the edge of the raster image.
3. At the Enter image clipping option [ON/OFF/Delete/New boundary]<New>: prompt, press ↵ to create a new boundary.
4. At the [Select polyline/Polygonal/Rectangular/Invert clip] <Rectangular>: prompt, enter P↵ or click Polygonal in the command‐line interface to draw a polygonal boundary.
5. Select the points shown in the top image in Figure 13.6 and then press ↵. The raster image is clipped to the boundary that you created, as shown in the second image in Figure 13.6.

As the prompt in step 3 indicates, you can turn the clipping off or on, or you can delete an existing clipping boundary through the Clip Image option.

After you clip a raster image, you can adjust the clipping boundary by using its grips:

1. Click the boundary edge of the raster image to expose its grips.
2. Click a grip in the upper‐right corner, as shown in the bottom image in Figure 13.6.
3. Drag the grip up and to the right, and then click a point. The image adjusts to the new boundary.
4. You can save the Rasterimport.dwg file for future reference and exit the file.

In addition to hiding portions of a raster image that are unimportant to you, clipping an image file reduces the amount of RAM the raster image uses during your editing session. AutoCAD loads only the visible portion of the image into RAM and ignores the rest. A triangular options grip enables you to flip the display between what is shown inside the border and what is shown outside.

Turning Off the Frame, Adjusting Overall Quality, and Controlling Transparency

You can make three other adjustments to your raster image: frame visibility, image quality, and image transparency.

By default, a raster image displays an outline, or a frame. In many instances, this frame can detract from your drawing. You can turn off image frames globally by typing Imageframe↵0↵. This sets the Imageframe setting to 0, which turns off the frame visibility. If it's set to 1, the frame is made visible. You can also set it to 2, which leaves the frame visible but doesn't plot it (see Figure 13.7).

Frames can also be controlled through the Frame flyout on the Insert tab's Reference panel. If you turn off a raster image's frame, you can't click the image to select it for editing, although you can still select an image using the All, Previous, or Last selection option (see Chapter 2, “Creating Your First Drawing,” for more on selection options). To make a raster image selectable with your mouse, turn on the image frame using the Display And Plot Frames or the Display But Don't Plot Frames option.

If your drawing doesn't require the highest‐quality image, you can set the image quality to Draft mode. You may use Draft mode when you're tracing an image or when the image is already of a high quality. To set the image quality, enter Imagequality↵ and then enter H for High mode (high quality) or D for Draft mode. In Draft mode, your drawing will regenerate faster.

High mode softens the pixels of the raster image, giving the image a smoother appearance. Draft mode displays the image in a raw, pixelated state. If you look carefully at the regions between the motorcycle and the background in the second image in Figure 13.8, you'll see that the edges of the motorcycle appear a bit jagged. The top image in Figure 13.8 uses the High setting to soften the edges of the motorcycle. You may need to look closely to see the difference.

Finally, you can control the transparency of raster image files that allow transparent pixels. Some file formats, such as GIF (Global Interchange Format), allow you to set a color in the image to be transparent (usually the background color). Most image‐editing programs support this format because it's a popular one used on web pages.

When you turn on the Transparency setting, objects normally obscured by the background of a raster image may show through. Select the raster image and then, in the Image tab's Options panel, select Background Transparency. You can also right‐click and select Image ➢ Transparency and then select On or Off from the Dynamic Input menu. In addition, you can enter Transparency↵ and then select the raster image that you want to make transparent. Press ↵, and then enter On or Off, depending on whether you want the image to be transparent. Unlike the Frame and Quality options, Transparency works on individual objects rather than operating globally.

The Properties palette offers many of the same adjustments described in this section. You can use it for quick access to the Transparency setting and other raster image settings.

Importing a PDF

To import a PDF, you use a method similar to the one you used earlier to import an image file. In fact, you could perform all of the steps in the exercise in the section “Importing a Raster Image” earlier in this chapter using a PDF file instead of the raster1.jpg file. You just need to know how to set up the Select Reference File dialog box to allow you to locate PDFs.

Try the following to see how to import a PDF:

1. Open a new file using the acad.dwt file as a template.
2. Use the Save As option in the Application menu, and save the drawing as PDFunderlay.dwg.
3. Click the Attach tool in the Insert tab's Reference panel or type attach↵ to open the Select Reference File dialog box.
4. In the Files Of Type drop‐down list at the bottom of the dialog box, select PDF Files (*.pdf).

   

5. Locate and select the SampleImport.pdf file.
6. Click Open to open the Attach PDF Underlay dialog box (see Figure 13.9). Notice that you have an option to select a specific page of the PDF document if you are opening a multipage PDF.

   

7. Click page 2 of the page preview on the left side of the dialog box.
8. Make sure the Specify On‐Screen options are selected for Scale and Insertion Point.
9. Click OK and then, at the Specify insertion point: prompt, place the outline of the drawing so that it is roughly centered in the drawing area and click.
10. At the Specify scale factor or [Unit] <1.0000>: prompt, use the cursor to scale the image so that it fills the screen (see Figure 13.10). Page 2 of the SampleImport.pdf file appears in the drawing.

Scaling and Osnaps with PDFs

In an earlier exercise, you were able to scale an image file, though you had to use a reference line that was already in the image file to scale the drawing roughly to its proper size in AutoCAD. If you have a PDF that was created from an AutoCAD file or from another vector‐based program, you can use osnaps to select exact locations in the PDF.

Try the following exercise to see how you can use osnaps to select geometry in the PDF. You'll scale the drawing so that the width of the stairs conforms to the known distance for that area.

First make sure the Snap To Underlays feature is turned on:

1. In the Insert tab's Reference panel, click the Snap To Underlays tool. Depending on your AutoCAD window width, you may see the icon only and not the “Snap To Underlays” label.

   

2. Select the Snap To Underlays ON option.

Now you are ready to scale the PDF drawing:

1. Click the Scale tool in the Home tab's Modify panel or type SC↵.
2. Select the attached PDF file and press ↵.
3. At the Specify base point: prompt, turn on the osnaps and select the left endpoint of the horizontal line near the top of the drawing, as shown in Figure 13.11.

   

4. At the Specify scale factor or [Copy/Reference]: prompt, type R↵ to use the Reference option.
5. At the Specify Reference length <1.0000>: prompt, click the same endpoint again or type @↵.
6. At the Specify second point: prompt, click the endpoint of the line shown in Figure 13.12.

   

7. At the Specify new length or [Points] <1.0000>: prompt, enter 196↵, which is the inch equivalent of 16′‐4″.
8. In the Navigation bar, choose the Zoom Extents option from the Zoom flyout to center the drawing in the drawing area.

In this exercise, you were able to use object snaps directly on the imported PDF drawing. You may have noticed that a tool tip appeared with the message “PDF (approximate): Endpoint.” The PDF drawing is not an exact representation of the original drawing, so the tool tip reminds you that even though you are using an osnap to select a location in the drawing, it is not an exact location as it would be in an AutoCAD file.

Controlling the PDF Display

You can take advantage of a number of other features of a PDF file. Just as with a typical Xref or image file, you can fade the PDF so that it appears as a background image. You can also use the Clip feature that you saw earlier in this chapter to clip the PDF to a specific area.

You can gain access to these and other PDF display features through the PDF Underlay Ribbon tab. This tab appears automatically whenever you select an attached PDF drawing. Click the PDF drawing of the lobby, and you'll see the PDF Underlay tab appear in the Ribbon (see Figure 13.13).

Table 13.2 describes the tools in the PDF Underlay Ribbon tab. The tools are fairly self‐explanatory. For example, the tools in the Adjust panel let you control the fade and contrast of the PDF drawing. The Display In Monochrome option displays a color PDF in monochrome.

One option that you'll want to take a closer look at is the Edit Layers tool in the PDF Layers panel. If the source PDF is a drawing that contains layers, you can control the visibility of those layers using this tool. With an imported PDF selected, click the Edit Layers tool to open the Underlay Layers dialog box (see Figure 13.14).

You can turn the visibility of a layer on or off by clicking the light bulb icon to the left of it in the list. For example, if you turn off the WALL layer in the Underlay Layers dialog box for the SampleImport example, the PDF drawing will change so that the walls will not be shown (see Figure 13.15).

Importing a PDF as an AutoCAD Drawing

PDFs can contain both raster and vector data. If you have a PDF that is a line drawing or 3D model, there is a good chance that it is stored in a vector format. PDFs containing vector information and text can be imported into AutoCAD as an AutoCAD drawing. For example, a PDF floor plan produced from AutoCAD can be imported back into AutoCAD and then edited as a normal AutoCAD drawing, as the following exercise will show:

1. Click the Open icon in the Quick Access toolbar, and open the PDFimport.dwg file from the samples folder. This is just a blank file with the units set to Architectural.
2. Open the Application menu by clicking the AutoCAD icon in the upper‐left corner of the AutoCAD window, and then select Import ➢ PDF. The cursor will change to a pickbox. At the Select PDF underlay or [File] <File>: prompt, press ↵.
3. In the Import file dialog box, browse to the Chapter 13 sample files and open the PDFvector.pdf file. The Import PDF dialog box appears (see Figure 13.16). Here you have a number of options that give you control over how the file is imported. For this exercise, you'll use the default settings.

   

4. Click OK. The PDF is imported into the current file as an AutoCAD drawing.
5. Click any object, and you'll notice that individual objects are selectable.
6. Click a room label. You'll notice that the text has been converted to lines.
7. Zoom into the left side of the drawing to enlarge the C and D grid lines.
8. Click the Measure tool in the Home tab's Utilities panel, and then select the endpoints of the grid lines between grids C and D. Notice that measurement is the same as the dimensioned distance.

This exercise demonstrates a few features of the Import PDF feature. In step 6, you discovered that the room label was imported as lines. For drawings that contain TrueType fonts, you have the option to import text in the original font. This will enable you to edit the text using the AutoCAD text editing tools. In step 4, you saw that the drawings imported to scale. The distance between grid lines C and D measured the same as the dimensioned distance.

The PDFvector.dwg file was created using the AutoCAD PDF (High Quality Print).pc3 printer option. In addition, it was plotted from model space. Had it been printed from a layout, measurements taken in the drawing would reflect the print size and not a full, 1‐to‐1 scale drawing. For example, measuring the distance between grid lines C and D would have returned a distance in inches as if measured from a scale paper drawing.

Be aware that PDF plots created from model space will lose some accuracy, even though they will import to a 1‐to‐1 scale. In addition, PDF drawings from other vector programs may not import to scale, in which case you can use the Scale option in the Import PDF dialog box to adjust the scale of the imported drawing. Or you can just scale the drawing after it is imported using the methods described earlier in this chapter.

Let's take a look at the options in the Import PDF dialog box shown in Figure 13.16. These options enable you to control how the PDF is imported. You can set whether raster data is imported into the drawing or, if the PDF contains layers, how the layers are translated. You can also control how types of geometry are converted. For example, in the Import Options section, you can set the PDF to be imported as a block or convert solid fills in the PDF to hatches. The options are fairly self‐explanatory, but a few may need a bit more explanation.

If the PDF file that you want to import contains multiple pages, you can select a page using the Page option just above and to the left of the preview image. You can also get a matrix view of the pages by selecting the thumbnail toggle above and to the right of the preview. The Options button in the lower‐left of the dialog box opens the Options dialog box to the File tab, where you can set the location for the storage of any raster images that are imported. (See Appendix B for more on the Files tab of the Options dialog box.)

Reconstructing Imported AutoCAD SHX Fonts

The PDF file format does not support AutoCAD's SHX fonts such as Simplex and Txt. When you export an AutoCAD file to a PDF, TrueType fonts are maintained as fonts but AutoCAD SHX fonts are converted to drawing geometry such as lines and polylines, so when you import a PDF that was created from an AutoCAD drawing, SHX fonts will be imported as lines and polylines.

Fortunately, AutoCAD offers the Recognize SHX Text tool that can recognize imported SHX fonts and convert them back to AutoCAD text (see Figure 13.17). To use this tool, go to the Import panel in the Insert tab and select Recognize SHX Text. You can also enter PDFSHXTEXT↵. Next, select the geometry you want to convert back to AutoCAD text. Try to avoid including non‐text geometry in your selection. Once you've selected the geometry to convert, press ↵. When AutoCAD is finished with the conversion, you see a dialog box telling you how many text objects were created and how many fonts were used.

AutoCAD also offers the PDF Text Recognition Settings dialog box, which enables you to determine the font that AutoCAD uses for the conversion (see Figure 13.18). This dialog box can be opened by using the Recognition Settings tool in the Insert tab's Import panel (see Figure 13.17) or by selecting the Settings command option in the Recognize SHX Text tool.

The PDF Text Recognition Settings dialog box contains a list that is populated with the most commonly used AutoCAD fonts. You can use the Add button to add other SHX fonts to the list, including custom and third‐party fonts.

Making Adjustments to the Map

As you can see from the previous steps, you can easily switch between an aerial view and a map view. You also have the option to show a combined aerial and map view using the Map Hybrid option or to turn the geolocation background off entirely using the Map Off option.

Finding Measurements and Distances

In the first Geolocation exercise, you may have noticed the Drawing Unit option in the Geographic Location dialog box. By default, this option is set to inches, but you can set it to feet, meters, miles, or some other unit of measure. By accepting the default inches for the Drawing Unit option, any measurements you take on the map will return distances using inches as the drawing unit. If the unit style of your drawing is set to Architectural, distances will be displayed in feet and inches—inches are the base drawing unit. Try the following exercise to see how distances are displayed:

1. Type Units↵ to open the Drawing Units dialog box.
2. Select Architectural from the Type drop‐down list, and then click OK.
3. Choose Map Road from the Map Aerial flyout in the Map Tools Ribbon panel.
4. Zoom into the map view so that it looks similar to Figure 13.23.
5. Choose Measure from the Home tab's Utilities panel.
6. Measure the distance from Laguna Street to Van Ness Avenue. The Measure tool reports a distance of 2446′, give or take a few feet.

In this exercise, the distance reported by the Measure tool is in feet. Had you not changed drawing unit in steps 1 and 2, the distance reported by the Measure tool would have been 29,043 units, which is the distance in inches.

You can use other methods to find measurements in your map. For example, you could get a rough estimate of the size of an existing building by drawing a closed polyline around the building outline (see Figure 13.24). Select the polyline and hover over a grip to view the dimensions of the outline closest to the grip.