Advanced Graphics Export

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Advanced Graphics Export

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Use Sketchpad to create images to paste into other programs — word processors, illustration programs, page-layout programs, and programs that create web pages. And use Sketchpad to produce illustrations for handouts, tests, and quizzes for your class, to illustrate articles or books about geometry or algebra, or to decorate your personal web site or a web site for your class or school.

This topic describes several useful tips and techniques that can help you produce attractive, high-quality images for such purposes.

Export Preferences

Hold the Shift key and choose Edit | Advanced Preferences | Export to control several settings that affect graphics export.

Arrowheads: Decide whether to include arrowheads on lines and rays.

Export Format: Export to the clipboard in bitmap format only or in both bitmap and vector formats.

Bitmap Scale: Export bitmaps at 100%, 200%, 400%, or 800%.

Vector Format and Bitmap Format

When you choose Edit | Copy, Sketchpad places a graphic image of the selected objects on the clipboard. The exported graphic on the clipboard can use a vector format or a bitmap format. Sketchpad normally puts both formats on the clipboard, allowing the program into which you are pasting to decide which format to use.

Bitmap Format: This format records the pixels that appear on the screen. In bitmap format, lines, circles, and text show stair-step effects (called aliasing); these effects are particularly visible when the graphic is enlarged, or when it's printed on a high-resolution printer. You can reduce the aliasing effect in a bitmap image by changing the scale for clipboard bitmap format.

Screen-capture programs also produce a bitmap format. This format is similar to Sketchpad's bitmap format, but the resulting graphic can also include objects such as window borders, menus, and the pointer.

On Windows, Sketchpad's bitmap format is DIB (Device-Independent Bitmap). For compatibility with some older programs, Sketchpad also creates a WMF (Windows MetaFile) which contains a DIB.

On Macintosh, Sketchpad's bitmap format is PICT.

Bitmap Format Exported at 100% scale
(Magnified 4x)

Vector Format: This format records information about how to draw objects like segments, circles, and captions, and can produce smooth lines without aliasing. Vector graphics are smoother and more accurate, and are usually the preferred format for word processors, graphics programs, and layout programs.

On Windows, Sketchpad's vector format is EMF+ (Enhanced MetaFile).

On Macintosh, Sketchpad's vector format is PDF. Use the Preview program or other graphics software to convert PDF to other formats.

Vector Format
(Magnified 4x)

Scaled Bitmap Export

When you choose Edit | Advanced Preferences | Export, you can set the scale used for bitmap export to 100%, 200%, 400%, or 800%. Use these settings to improve the quality of exported bitmap graphics when you're exporting to a program that doesn't recognize vector formats.

By using a higher scale, you can reduce the stair-step effect (called aliasing) that occurs with bitmaps. Set this to more magnification if you’re copying bitmaps from Sketchpad to paste into a document in a word processor or page layout program that you intend to use for high-quality production. The result will be a larger graphic that includes more pixels. After you paste it into a word processing, page layout, or other application, you can scale it down to produce a higher-quality image of the desired size.

For instance, say you want use a 600 dpi printer to print a document containing a small Sketchpad graphic that is 50 pixels wide on the screen, and you'd like the printed graphic to be 0.2 inches wide. If you export the graphic at 100% and look closely at the document, you will be able to see the aliasing.

To improve the quality of the printed image, you can determine the appropriate scale for bitmap export. The number of pixels in the printed image will by 600 dpi * 0.2 in = 120 printer dots. Divide the number of desired printer dots by the number of screen pixels: 120 / 50 = 2.4. This corresponds to a scale of a little more than 200%, so you should use the Export Preferences panel to set Scale for clipboard bitmap export to 200%. The images below show magnified views of the printed document using the original export scale of 100% and the calculated scale of 200%.

Bitmap Format Exported at 100%

Bitmap Format Exported at 200%

Crop Exported Graphics

Lines and rays extend far beyond the limits of the screen. Depending on the specifics of a sketch, other objects, particularly loci and function plots, may have similar extents. But when you copy such objects, you don’t want an image of infinite size. Accordingly, if an image being copied extends beyond the edges of the window, Sketchpad crops the image to the window dimensions.

Use this behavior to control the exact extent of the image copied to the clipboard. Before copying, resize and scroll your sketch window so that it shows the desired portion of the sketch. When you choose Edit | Copy, the clipboard image will be correctly cropped.

Graphics Document Export

Sketchpad normally exports graphics directly to the clipboard, for ease of pasting into word processing and page layout applications. If you like, you can preserve the exported graphic as a separate vector-graphics document on your computer, either using EMF+ (Enhanced Metafile) in Windows or PDF (Portable Document Format) on Macintosh.

Windows: Choose File | Save As. In the Save As dialog box, choose Enhanced Metafile (*.emf) from the Save as type list. Then name your document and click Save. The resulting EMF+ document can be imported by many other Windows programs. The exported document includes all objects that appear within the window. Use the edges of the window to crop the exported graphics. Once you've saved the EMF+ document, there are a number of commercial graphics programs that can convert the EMF+ document to other graphics formats such as EPS or PDF. Depending on your printer driver, you may also be able to create a PDF document directly, by printing from Sketchpad and specifying PDF output in the Print dialog box.

If you want to export some but not all of the visible objects, use the Copy command.

Macintosh: Select the objects you want to export and choose Edit | Copy to put a vector format (PDF) image on the clipboard. Then open the Preview application, and choose File | New from Clipboard to display the contents of the clipboard in a new PDF document. Save the document, either in its original PDF format or in any of the other formats Preview supports. You can also create PDF and Postscript (PS) documents by choosing File | Print and using the PDF button in the Print dialog box.

Once you've saved a PDF document, there are a number of graphics programs that can convert the PDF document to other graphics formats such as EPS.

Screen Captures

You can create a bitmap graphic of the entire Sketchpad window, including even menus and the cursor, by using the screen capture capabilities built into Windows and Macintosh.

Windows: Press the Print Screen key to capture the entire screen, or Alt+Print Screen to capture the active window. The result is a bitmap on the clipboard; you can paste this bitmap into any program which recognizes bitmap files.

Macintosh: Press -Shift-3 to capture the entire screen, or -Shift-4 to capture part of the screen. The result is a picture on your desktop. Use the Preview program to change this picture into any common graphics format.

Hold the Ctrl key while pressing the other keys to put the captured picture on the clipboard instead of the desktop.

For more capture options on Macintosh, use the Grab program.

Screen captures are excellent for showing what the entire screen looks like and for including a menu or the cursor in your graphic. But a screen capture does a crude job on Sketchpad constructions. Diagonal lines and circles look jagged and blocky, text is of poor quality, and resizing the graphic may give unexpected results. For better results with Sketchpad constructions, use Sketchpad itself to copy the objects you want by selecting the desired objects and choosing Edit | Copy.