About preparing raster data for vectorization

The effort required to prepare raster data for vectorization varies from one image to another. In some cases, the input raster may need only minimal changes or no changes. However, there can be instances when you need to perform a fair amount of editing to get the raster in a condition that is viable for conversion. With ArcScan, you can carry out these operations without leaving the ArcMap environment. Below is an overview of the ArcScan raster cleanup.

The cleanup session

ArcScan employs a cleanup session similar to that of the ArcMap edit session. You must start a cleanup session to activate the commands that are available in the Raster Cleanup menu as well as the tools located on the Raster Painting toolbar. All edits made to the raster can only be performed during an active cleanup session. You can stop the cleanup session once you have completed the raster editing tasks. Upon stopping, you will be prompted whether to save changes to the raster.

Noise and feature removal

One of the most common tasks performed with the Raster Cleanup tools is the removal of raster cells. This can involve deleting noise or elements that represent information in the raster. Noise can include speckles that result from the scanning process or imperfections in the original source document that were scanned. Features can include cells that represent text, points, lines, and polygons.

There are a few ways to remove cells from the raster. These include erasing one pixel at a time and erasing a series of connected cells using the Erase and Magic Erase tools on the Raster Painting toolbar. On a broader level, you can use the Erase Selected Cells command to eliminate the currently selected cells. This technique requires the use of the raster selection tools and can help make the cleanup process more efficient. Whether your raster cleanup requirements are small or large, ArcScan has the tools to help you complete the job.

Adding new cells

You can add new cells to the raster using the tools that are available on the Raster Painting toolbar. You can use the Brush, Fill, and Draw tools for these tasks. The draw tools are line, rectangle, polygon, and ellipse. You can change the size of the brush as well as the width of lines. This allows you to create a variety of geometric shapes in your raster. All the tools described create new cells in the current foreground color. However, you can switch the foreground and background colors by clicking the Swap Foreground/Background button on the Raster Painting toolbar. The Raster Painting toolbar's cell creation tools behave much like the tools found in other popular graphics programs. This design allows you to utilize drawing techniques with which you may be familiar.

Saving raster edits

Edits that were performed during the raster cleanup session can be saved directly to the original raster layer. Alternatively, you can save changes to a new raster file. This allows you to make all the changes you want without affecting the original source raster. You can save your raster edits during the cleanup session or when you are finished. If you have not saved your edits prior to stopping the cleanup session, you will be prompted to do so at that time. However, you do not have to save changes to apply them to the vectorization. You can make your changes, vectorize your data, and discard the edits if necessary.

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Published 6/8/2010