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Smart Drawing Conversion

GTX Intelligent Paper to CAD Solutions

Andrew Johnson

Scanning and vectorisation of drawings has come along way in the last few years. GTX conversion software is preceded by it’s reputation and even with high expectations, Andrew Johnson was delighted and surprised with what he found.

As little as 3 years ago, vectorising software was very basic and could really only convert simple lines that did not cross other lines. This saved considerable time for specialist tasks such as digitising contour lines on maps and charts. In these special cases, many man-hours could be saved if the right conditions were met. But in most cases, real world drawings were beyond the software and people were better off scanning the drawing into a form that allowed them to draw over the top of on the computer a process known as "heads up digitising" -- virtual tracing in CAD over a simultaneous image display. Recognising objects such as text was simply out of the question.

Today’s offerings are far more sophisticated and modern software includes:

• Elaborate raster editing tools. Archiving, editing and reissuing raster based drawing is within everybody's reach and is very cost effective in most cases
• Intelligent Character Recognition (ICR) with font training ability for the intelligent conversion of text
• Automatic batch processing for unattended conversion of large numbers of drawings
• Sectional, multi-stage conversion of a single drawing using the most appropriate technique for different parts of a drawing
• Hybrid drawing management, enabling raster images and a vector image to be used together like a single drawing

GTX offers two streams of programs. The GTXImage stream starts with a raster only editing program in its base-level offering, GTXImage Edit. GTXImage CAD, GTXImage CAD Plus and GTXImage /GTXICR Plus contain progressively more powerful raster editing tools and a stripped down version of AutoCAD for vector editing.

GTXRaster, the other stream, is offered as an AutoCAD "bolt on". It requires the user to have an existing AutoCAD license for the GTX application to work. Entry level starts with GTXRaster CAD with GTXRaster CAD Plus for the more demanding user. GTXICR Plus is offered as a text recognition option for GTXCAD Plus. The pricing begins at A$2,000 for the raster only GTXImage Edit and progresses to A$10,000 for GTXRaster CAD Plus with GTXICR Plus option.

I ran my tests using the top of the line versions of each stream. These versions have all the same functions as the lighter weight versions. Tests were run on a Pentium 200MMX, 64Mb RAM, 3.2 Gb IDE hard disk with a Matrox Millenium I graphics card.

Getting Started
The installation of both GTX/Image and GTXRasterCAD Plus took less than half an hour each. The only one minor problem arising during installation was the discovery that the "bolt on" versions need to have the AutoCAD ACAD.MNU file compiled in order to access GTX commands within the AutoCAD editor.

One of the great things about GTXImage was the way it left my special setup for PMS-View drawing database software alone and automatically gave me another completely different setup for the raster editing trials. By exiting GTXImage, I could return to my other configuration by clicking on my old shortcut.

The GTX programs take up to 20 Mb of hard disk space each.

GTX Tutorials
I immediately felt at home with this software because it functions within an AutoCAD environment. The tutorials are easy to follow and within a short time you get to know most of the commonly used tools.

You can work through the tutorials in less than an hour covering the three key topics.

Raster cleanup
De-speckling, de-skewing, cropping, scaling and raster smoothing. Also combining vector data and merging back to a single raster file.

Raster editing
Cutting & pasting, Intelligent Object Picking (IOP) i.e. picking lines and circles etc for manipulation as if they were a CAD entities. Re-scaling, multiple raster layering and AutoCAD style snapping for raster objects such as line intersections.

Raster to Vector Conversion
Hybrid drawing management. Manual, automatic and selective vectorisation. Intelligent Character Recognition (ICR).

Unfortunately, this is where the instructions on technique stop. There is scope for further education in this field. There must be many users teaching themselves the same basic techniques for clever conversion by their own experience all of whom could save days or weeks if some of these procedures were outlined in more detailed tutorials.

The manual provides a well laid out function reference and a quick scan reveals a rich set of tools is provided.

GTX Tools
The aim of the software is to provide the tools required to carry out the three tasks listed above.

The tool set is feature-rich and makes these tasks very "do-able". The benefit of using software to automate conversion is in the time and effort saved over basic redrafting.

GTX software can save time and effort in most cases. It is very productive for raster cleanup, editing and "heads up digitising". There are no equivalents within conventional CAD packages. Raster to vector conversion is also handled well, but with the following qualifications. It is no better than redrafting when:

• Lettering containing letters that touch other letters.
• Very faint images that contain gaps and missing lines.
• Congested areas where lines cross each other at small angles or at close centres.

In some cases, when objects are very crowded, cross or touch other objects or the scan is poor, there will be little or no benefit in automating conversion.

Having said that, if your drawings contain mainly clean, neat lines and discrete text, this software will save many hours. In real world drawings, there are areas of drawings that will benefit enormously and areas that won't. The upside is, that after you have finished converting the easy bits, you don't have to change environments to redraft the hard bits.

GTX’s Intelligent Object Picking (IOP) lets you pick objects as if they were CAD entities. Raster snap tools allow you to snap to the ends of a line and then operate on them i.e. move, delete, rotate or scale etc.

Selecting objects in the raster images with GTX’s IOP simplifies editing and cleanup.

For raster to vector conversions, the tools work well provided the right technique is used.

For the straightforward, clean drawings you can try selecting the whole raster image and vectorising the image in one hit. This will convert text as lines and thick walls etc. will be replaced by a single thin line.

Unfortunately, there was nothing in the basic tutorial exercises on technique for difficult areas. To unravel the congestion in some drawings, you need to convert certain things first so that they don't get in the way of other objects. To illustrate this, here is the technique I used to unravel a congested part of an architectural drawing:

• Deskew scan to correctly align horizontal and vertical lines for better interpretation.
• Crop scan to remove unnecessary peripheral elements
• Set up vector layers for destination of the entity categories
• Convert lines, circles etc. over congested areas first using IOP. and move to appropriate layers. As these entities are converted, remove underlying raster to unclog the area. Repairs to remaining raster occur automatically but should be scrutinised to ensure correct recognition of remaining raster entities in later steps. Some repair might be necessary
• Save temporary raster file here to come back to if necessary
• Select and vectorise text. At this time may need to tune text recognition software and train a font. Once tuned, reload raster from step 5 if necessary and run text conversion on selected text raster, erasing the raster as you go
• Pick any solid areas that need to be outlined. Fill in white holes. Raster outline the solid. Smooth the edges. Vectorise the edges. (See figure 2 for example of this work)
• Save raster and vector to temporary files again
• Complete the conversion by using progressive vectorisation and raster removal on remaining areas or if suitable automatically vectorise remainder

Devising a planned procedure for your drawing conversion will help you get the best efficiency from the tools available and enable your conversion team to follow a clear, consistent process.

Pats on the Back
Some of the very nice features found in GTX software include the intelligence of the IOP tools, the ability to progressively vectorise raster, being able to go back and repeat stages by recalling temporary files, the hybrid drawing management, ICR training capability and the native AutoCAD DWG vector file format. For existing AutoCAD users, this program is easy to learn. I really liked the look and feel of the software and appreciated being able to stay in the one program to edit/convert and review the CAD results.

All the GTX raster editing commands are based on AutoCAD’s commands for vector i.e. "gsave" to save the raster file, "gerase" to erase some raster and "gmove" to move some raster. A nice touch.

Wish List
As always, there are some tools I would like to see added the GTX suite including:

• The ability to recognise the edges of a thick object such as a solid brick wall and treat it differently from a thin object such as a line. This way, you could have lines vectorised into centre lines and solid objects reduced to outlines.
• Adjustable sliders that let you preview how certain thicknesses of line will be interpreted during conversion into CAD. These sliders would be used to get the best match of .25, .35, .5 etc. lines.

The indexes are light on for detail. I found many of the terms used in the books were not to be found in the indexes. Since indexing is an automatic process these days, someone must have given a high priority to saving paper.

The conversion of raster to vector is presented using a "black box" approach. Many settings for adjusting gaps to be jumped, the maximum and minimum radius of circles to use, the extension of lines to neighbouring lines etc. are not adjustable. I can understand the desire to hide complicated stuff from the new users, but such settings could be hidden behind an ADVANCED button with a reset of default settings button in the unlikely event of a profound maladjustment of controls.

On the bug side, I found it annoying that the software tried to recognise arrow heads in many places and this feature could not be turned off. This problem occurred on both the GTXImage and the GTXRaster versions of software. GTX advises this feature will be addressed soon.
(Recognition of touching letters in text, line gaps and arrowhead recognition during the conversion process have all been addressed in the latest version - Ed)

Occasionally, a piece of a polyline would break out and move itself typically 5mm to the side of the rest of the line. This bizarre undocumented feature occurred in both of the GTX programs loaded.

These bugs were reported by email and response/acknowledgment came from UK customer support. "...these features will be fixed in the next revision..."

Who Needs This Software
Raster drawings will be with us for a long, long time. There are still many people creating drawings with pen and ink. There are many CAD users who alter drawings after plotting, and more still who transmit drawings to clients in paper form only. There are vast storehouses filled with paper drawings that contain valuable information needed for on going reference. A proportion of these could be reused economically if small alterations could be made and the drawings reissued. For these reasons, this sort of software will continue to assist in bridging the gap between hand drawn and CAD based drawing systems.

Incidentally, anybody still drawing by hand should review their drafting style to ensure the best automatic conversion of their drawings at a later date. Small changes to the drawing layout can make big differences in conversion efficiency.

Learning a sophisticated program that tackles the complex tasks of raster editing and vectorisation takes time. Any office already using AutoCAD and needing this capability is going to save a lot of training time, using a product already familiar to them. The vector files coming out of the software are not based on a third party approximation to a DWG file they are the genuine article. There are some other very good programs on the market, but they certainly don't look and feel like AutoCAD. If another program had some better features for your particular application, you would have to weigh that up against the retraining time.

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