Never Digitize Again! Converting Paper Drawings to Vector

Transcription

1 December 2-5, 2003 MGM Grand Hotel Las Vegas Never Digitize Again! Converting Paper Drawings to Vector Felicia Provencal GD42-3L How many hours have you spent hunched over a digitizing board converting old paper drawings into AutoCAD drawing files? With the tools provided in Autodesk Raster Design, you may never need your digitizing board again! In this lab, we will look at some of the techniques for scanning paper drawings and converting those scans into usable vector files. You will also learn how to convert text in a scanned image into AutoCAD text entities, and extract this information for use in word processing and spreadsheet programs. About the Speaker: Felicia is an Independent Consultant based in Hawaii with more than 17 years of experience working with AutoCAD, AutoCAD Map, Autodesk Land Desktop, Autodesk Civil Design, Autodesk Survey, Autodesk Field Survey, and Autodesk Raster Design software. She writes the monthly tutorial on civil software products for Point A Toplines. A popular Autodesk University instructor, Felicia conducts workshops and seminars and provides consulting and training services throughout the United States and the Pacific Basin. felicia.provencal@k-teksolutions.com

2 In this class we will take an in-depth look at the Vectorization Tools in Autodesk Raster Design. All of the legacy vectorization tools, including the old LFX module were completely retooled for CAD Overlay release 2000i, and new text recognition tools were added in Raster Design R3. First, we will start off by performing a quick conversion. There are two types of vectorization tools: Interactive Conversion tools and Follower tools. These tools are used to convert raster linework to vector objects. Note that for full functionality, the Vectorization Tools should only be used with bi-tonal (or strictly black and white) images. Not all of the features will work with grayscale or color images. The first type of vectorization tool provided by Raster Design is the interactive vectorization. These tools convert standard raster geometry into their vector equivalent using single picks or multiple picks to determine the appearance of the new vector objects. These are called interactive vectorization tools because you can verify and change any of the dimensions found by the commands before actually generating the vectors. There are three linear vectorization tools available: Line, Polyline, and Rectangle. All three of these tools use the options such as SmartCorrect, Single Pick, and Multi-Pick, to generate vector lines, polylines, and rectangular, closed polylines from detected raster information. Note that the Polyline command draws straight-line segments only (no arcs) and does not have a Single Pick option. Some polyline conversions are handled best by the polyline follower described later. 1. Start Raster Design and open the RD drawing. 2. Go to the Image pull-down menu, then pick Vectorization Tools, then Line. Select a point on the line at the bottom of the mechanical part. Once you have selected a point, you will see a starting point arrow as well as a temporary vector showing the extents of the line selected. Also note that the current length and angle of the selected line are displayed. 3. Type L for Length at the prompt. Enter 13.3 for the length of the line. Press Enter to exit. The line will then update to match the entered length and the underlying raster will be removed. All values of selected geometry can be edited this way. Next, let us take a closer look at the controls that drive the full functionality of the Vectorization Tools. Understanding the various settings and their effects will help you get the most out of the software. There is a lot of power in these tools, much of which will be lost if the settings are not made correctly. The Options that control the vectorization tools are divided between three tabs in the Raster Design Options dialog box. 4. Go to the Image pull-down menu and choose Options. Click the Raster Entity Detection tab. The first tab we will look at is the Raster Entity Detection tab. The settings on this tab control how Raster Design recognizes which raster elements are part of the linework it should convert. This includes recognizing linework with gaps, such as contour lines and utility lines, and non-continuous linework, such as dashed or dotted linetypes. This tab is divided into three sections. The first section controls the single pick options. Single pick is where you can click once on a piece of raster linework, and the program will automatically determine endpoint conditions, radii, and direction. Options include max jump length which determines how big a gap in the linework is acceptable. Again, this is typically used for utility lines and contours. You can also set options to stop at raster intersections and use raster pick gravity. The stop at raster intersections option will force single pick lines, arcs, or polylines to end where an intersection with other raster data is encountered. The raster pick gravity option is similar to the AutoCAD Aperture setting. 2

3 The next set of Raster Entity Detection options control how multi-pick operations behave. The only option in this section is the float tolerance. This affects how close the pick points must be to the raster for determining end point conditions. The third section of this dialog box determines how the vectorization tools recognize non-continuous linetypes such as dashed or dotted ones. The max dash length determines the longest possible dash in pixels and the max blank length determines the longest possible gap between dashes in pixels. Any lengths for the options in this dialog box can be selected using the Pick button. 5. Choose the VTools General tab. The next tab in the Options dialog box that affects the Vectorization Tools is the VTools General tab. These options control how the vector geometry is created and what happens to the raster. The first section is the raster Removal Method options. You have three choices: none, rub, and REM. If you choose none, the underlying raster is left untouched. If you choose rub, all raster below the new vector will be removed. If you choose REM, only the raster relating to the vector object created will be removed. Any intersecting raster paths will be left untouched. This is very useful when converting mechanical part drawings or architectural floor plans where there are many intersections between geometry. The next group of settings is typically used for the Interactive Conversion tools such as the line we just converted. The verification list is used when converting lines and arcs. You can right click when converting these types of raster data and a list will appear with the most recently used or most frequently used values for lengths and angles. This group of settings also contains two toggles: Stop at vector intersection and Display start point glyph. The Stop at vector intersection option will force newly created vector objects to terminate where other vector geometry is encountered. This is often used in floor plans and parcel maps to ensure that converted raster data does not extend past previously generated vector. The existing vectors themselves may have been created by any of the vectorization tools. The Display start point glyph option will show an arrow head that points in the direction from the start point to the end point of the newly created vector object. This is useful when determining how changing the length or direction in the verification process will affect the new vector. 3

4 The last group of settings in this dialog box affects the SmartCorrect capabilities of the Interactive Vectorization commands. SmartCorrect will adjust lengths and angles based on these settings. The connection tolerance settings will adjust lengths and angles within the tolerance specified either by the AutoCAD APERTURE setting, or an entered amount in AutoCAD units. This means that the new vector object can be displaced from the original raster by these amounts to honor constraints in lengths and angles (such as keeping lines orthogonal). The Respect Drafting Settings toggle will either use the settings from AutoCAD drafting aids such as SNAP, ORTHO, OSNAP, and POLAR, or not. The Round values settings can force new vector linework to use lengths and angles that are rounded to the AutoCAD precisions or custom values. We will discuss the Vector Separation button during a later section of this class. 6. Click OK to exit the Raster Design Options dialog box. We will now continue to convert another part of this design. There are four interactive vectorization tools that convert non-linear raster data into their equivalent vector objects. The Circle and Arc tools also use the options described previously, such as SmartCorrect, Single Pick, and Multi-Pick, to generate vector circles and arcs. The Text and Multiline Text commands can be used to interactively replace raster information with AutoCAD single line text and AutoCAD multiline text, however, you will have to retype the text. We will show you how to use the new text recognition tools in the last section of this lab. 7. Go to the Image pull-down menu, then pick Vectorization Tools, then Circle. Select a point on the circle at the center of the mechanical part. 8. Type in R for Radius and enter a radius of Press Enter to exit the command. Since we have chosen a Rub removal method for the underlying raster, note how the intersecting lines are left intact. Another type of single pick conversion can take advantage of the non-continuous linetype settings in Raster Design. 9. Go to the Image pull-down menu and pick the Options command. Go to the Raster Entity Detection tab and pick the Pick button for the Max Jump Length setting. Pick two points representing the width of a gap in the dashed arc located beneath the part. If necessary, set the Max Jump Length to 15. Click OK to exit the Options dialog box. 4

5 10. Go to the Image pull-down menu, then pick Vectorization Tools, then Arc. Pick a point on the arc below the mechanical part. Press Enter to exit the command. The Max Jump Length setting controls the spacing used by the software to recognize and bridge gaps in a line, circle, polyline, or arc. This can be used to cross the space left by labels, poor quality originals, or dashed linetypes. The next type of Vectorization tool we will examine is semi-automatic vectorization. These are also known as the followers and can be used to convert polylines, contours, and 3D polyline breaklines very quickly and easily. The Polyline Follower is the most obvious replacement for CAD Overlay LFX tools. This command has several new options built into the command. You now only need to pick one point on the raster, and it will follow the raster data in both directions until it reach and end point or decision point. You may use raster snaps to more accurately select points on the raster, and you no longer need to set a work area. The entire extents of the image will be used, unless the partial option is chosen. The polyline follower can also follow vector line or polyline data as well as raster data. This extremely useful when a portion of the image has already been converted previously, or the extents of the project is delineated with a vector polyline. You can switch follower ends to bridge gaps found at either end of the new polyline, or to join to an existing vector. You can close the polyline back to the starting point (even if it is outside the close tolerance set in the Raster Design Options dialog box). You can backup along the polyline one segment at a time, or rollback to any vertex previously found by the follower. You can end the current polyline and start following another raster segment without having to restart the command. You can choose a point to show the follower the correct path when a decision point (or confusing area in the raster data) is reached. You can also join the polyline being created to any other existing vector. 11. Open the RD drawing. We will use this example to show the polyline follower as well as the vector separation tools. Before converting the raster linework, we will need to set some of the options for the dashed line recognition as well as the vector separation. 12. Go to the Image pull-down menu, then pick the Options command. Make sure the Raster Entity Detection tab is selected. Set the Max Jump Length to be 55, the Max Dash Length to be 30, and the Max Blank Length to be Pick the VTools Follower tab. The settings in the VTools Follower tab primarily affect the new follower tools that have replaced the older LFX module. These are the Polyline Follower, Contour Follower, and 3D Polyline Follower. 5

6 The first group of settings controls the basic follower parameters. The Follower Color is the display color used to show the path the follower is taking. This may need to be changed if the image color conflicts. If the Pan to decision point option is turned on, when a decision point is encountered, the follower commands will automatically pan to that point so you can choose the correct path, or end the follower. A decision point is wherever a raster intersection is found where there is no obvious direction to follow. The End current polyline if closed loop is detected option will force polylines to close when the end point is within the specified tolerance in pixels of the start point. The Post process points option controls how closely the resultant vector hugs the original raster. A high deviation will result in a polyline containing fewer points and being less faithful to the original raster. In contrast, a low deviation will result in a polyline with more points that more closely matches the raster path. In either case, the post processor will decide where to distribute the points along the line usually placing more points in bends than in straight sections. The second group of settings controls how the Contour Follower command operates. The Contour creates setting determines whether the contour follower creates Polylines or Land Desktop contour objects. The Elevation option controls how elevations are assigned to the contour. There are 5 options for elevation assignment: using the AutoCAD ELEVATION value, setting all contours to elevation zero, using the preset elevation, prompting for elevations using a default calculated by the interval setting, or setting an elevation by using existing vectors. The last section of this tab contains settings that control the creation of 3D polylines using the 3D Polyline Follower. The Elevation interval option controls the default values of elevations for each vertex or intersection with raster geometry the 3D polyline follower encounters. The Use raster impact points only option will force the 3D Polyline follower to generate information only at the points where the follower encounters raster information. Any vertex from an existing vector polyline or selected points will be ignored. The Ignore raster speckles option will allow the 3D Polyline Follower to skip over any raster data that may be a result of a dirty original. 14. Choose the VTools General tab, then pick the Vector Separation button. This will bring up the following dialog box. 6

7 This dialog is divided into two tabs: General and Contour. We will discuss the Contour tab later when we learn about the Contour Follower. The settings from the General tab allow you to specify layer and polyline width settings for vector created by any of the Vectorization Tools commands. The layer assignments are based on the type and width of raster. Vectors can be placed on a preset layer, the current layer, or you can be prompted for a layer selection. Polylines, contours, and 3D polylines can use the current AutoCAD setting for the polyline width (PLINEWID), the actual width of the detected raster data, or zero. The Width table section of the Vector Separation Options dialog box can be used to set ranges of widths and how layers will be assigned to each range. This is very useful when dealing with topographic maps or architectural floorplans where the lineweight is used to determine the type of line drawn. For example, foundation walls may be drawn with a different width than interior stud walls. You can also use layer and polyline widths for non-continuous raster data. The settings from the Raster Entity Detection tab shown previously control how the vectorization tools determine what is a non-continuous linetype. There are default settings that can be used in place of the width table and non-continuous linetype detection, or to control layer settings of those objects that do not meet any of the width or linetype conditions. 15. Toggle the check box to Use the Width Table. Pick the Insert Below button to add a line to the width table. Click the Query Width button and select one of the utility lines to determine the width in pixels. Set the first width range to use a maximum value of 4, the layer UTILITIES, and a polyline width of Zero. 16. Pick the Insert Below button again to add a second width range. Set the layer to be *PROMPT* and the polyline width to be Actual. 17. Toggle the check box to Override Width Table for Non-continuous Entities. Set the layer to be EASEMENT and the polyline width to be Zero. 18. Pick the OK button to exit the Vector Separation dialog box. Pick the OK button to exit the Options dialog box. 19. Go to the Image pull-down menu, then pick Vectorization Tools, then pick Polyline Follower. Click on the lower easement line, then press Enter to exit the command. 20. Repeat the command for the lot lines and utility lines. 7

8 Note how the vectors are placed on the requested layers automatically. The polyline follower is generally used to trace linework where length, radius, and direction are not important. This is typically used for borders and boundaries. For elements where more accuracy is required (such as the lot lines), use the Line, Arc, and Polyline tools discussed previously. In addition to all the features used by the Polyline Follower, the Contour Follower has the following new features. There are now more options for setting elevations than supported by LFX. We saw these when we discussed the Contour option from the VTools Follower tab in the Raster Design Options dialog box. Layers can now be set using options from the Contour tab of the Vector Separation dialog box. Also, contours can respect the settings used by Land Desktop such as layer creation, layer assignment, and contour styles. 21. Open the RD drawing. 22. Go to the Image pull-down menu, then choose the Options command. Select the VTools Follower tab and change the elevation interval to be 20. Note that you can also use Land Desktop contour objects for the contour following. You must have Land Desktop installed on your system to use this option. 23. Choose the VTools General tab, then pick the Vector Separation button. Select the Contour tab. This will show the following dialog box. In the Vector Separation Options dialog box, the Contour tab controls the assignment of contour layers. You can either enter layer width assignments similar to those used by the Width table. These assignments are based on a contour elevation increment. Or you can use the settings provided by Land Desktop. 24. Change the Minor Interval to be 20 and the Major Interval to be 100. Set the Minor Layer to be CONT-20 and the Major Layer to be CONT Click OK to exit the Vector Separation dialog box. Click OK to exit the Options dialog box. 8

9 26. Go to the Image pull-down menu, then pick Vectorization Tools, then pick Contour Follower. Click on a contour line. When the follower reaches the end of the contour, press Enter, then type in the contour elevation. Choose another contour line. Note how the default elevation updates based on the interval. Also note how the contours are separated to different layers based on the assigned elevations. For the last part of this class, we will take a quick look at the text recognition tools introduced with Raster Design 3. The new text recognition tools allow you to extract raster text information as AutoCAD text objects for use within the current drawing. The text recognition tools can also be used to export scanned text to an external text file, or tables and schedules to external spreadsheet files. There are two types of text that can be converted: text and table text. Text that represents labels, sentences, or paragraphs are treated as standard text and can be converted to AutoCAD Text or Mtext entities. Items such as construction notes, call-outs, or specifications are considered to be standard text. Text of this type can also be exported to an external text file. Standard text is converted using the Recognize Text command. Text organized into a schedule or chart is treated as table text and can only be converted into individual AutoCAD Text entities. Items such as door schedules and curve tables are considered to be table text. Text of this type can also be exported to an external spreadsheet file. Table text is converted using the Recognize Table command. 27. Open the RD drawing. 28. Go to the Image pull-down menu, then pick Text Recognition, then Recognize Text. 29. Click below and to the left of the existing notes. Press Enter to use a rotation angle of 0. Window the notes to be converted. The command will then display the verification dialog box. This dialog box is used to review and edit the text before it is brought into the current drawing. 30. Change the registered trademark symbol to the letter B. Click OK. 9

10 The text is then converted to AutoCAD multi-line text. The text recognition tools are looping, so you must cancel the command to get out. 31. Press Esc to exit the command. We will now convert a table to a spreadsheet file to show you how the export capabilities of the text recognition tools work. 32. Open the RD drawing. 33. Go to the Image pull-down menu, then pick Text Recognition, then Recognize Table. 34. Click below and to the left of the existing schedule. Press Enter to use a rotation angle of 0. Window the schedule to be converted. 35. When the Verify Text dialog is displayed, click the Export button. Navigate to the My Documents folder to save this file. Click Save. 36. Click Cancel to exit the Verify Text dialog, then press Esc to exit the command. 37. Start Microsoft Excel, and open the file we just created. This can be a very handy tool for adding bill of material information to a spreadsheet for use in creating cost estimates. Any type of chart can be converted to a spreadsheet, and any block of text can be converted to a word-processing file using the Recognize Text command. 10