Export Operations

PlansPlus offers three styles of file export, bitmap (BMP), portable network graphics (PNG) and metafile (EMF) files.

Device independent bitmap files (they use the filename suffixes .bmp or .dib) are the basic Windows file types for picture data. They have the capability of using several different color depths, from monochrome to true color, capable of more then 14 million colors. Bitmaps have a fixed pixel width and height, and therefore are sized differently on different media where the size of pixels differs. For example, a bitmap displayed on a screen is nominally displayed at 72 pixels per inch (it can be more or less depending on the screen's physical capabilities and the resolution that is being used to display). A printer, on the other hand, may print at 300 to 1200 pixels per inch, so a bitmap that may display on the full screen size will look like a postage stamp when printed without any other manipulation.

Portable Network Graphics are derived from bitmaps, and they alleviate many of the problems that bitmaps have. They are compressed graphics, so they take up less space (sometimes a lot less space), and unlike bitmaps they are directly usable on the world-wide web, like GIFs and JPGs. They are considered more advanced than GIFs because they can handle true color graphics, while GIFs are limited to 256 color, paletted graphics, and they don't have the legal shortcomings that GIFs have. Unlike JPGs they do not use a lossy compression, so they don't degrade with handling.

The metafile export (file type .emf, standing for extended metafile format) is of a different type than a bitmap. This export contains vector data that can be used to rebuild the bitmap at another location when it is viewed. Since all monitor types in common use are bitmapped devices, EMF's cannot be displayed directly, but must be converted from vector to bitmapped format for display. This export therefore which contains no intrinsic sizing data; that data is instead supplied when the file is viewed by any software that can handle metafiles (like Paint Shop Pro) and do the conversion, independent of Punch! and PlansPlus.

All the export types are controlled by a single export dialog:

With this dialog the user may control the scope and resolution of the exported file. The scope section is exactly like that for the printer. There are three scope choices: The whole plan, that part of the plan visible on the PlansPlus screen, and a lassoed rectangle (the lasso action, done by dragging the mouse, must be done before invoking Export; if it isn't, that choice will be disabled). The three boxes to the right of the choices show the size of teh choice rectangles, in inches or millimeters.

The next section describes the format of the exported file. The only choice here is the type of export that is desired, and the choices are Bitmap (.bmp), Portable network graphics (.png) and Metafile (.emf). There is a display box showing the color depth that will be delivered; it is determined by the color depth of the system monitor.

The final section is Resolution, in which the user describes the resolution that is to be used to create the graphics. Since the metafile format choice has variable resolution, when that choice is made the entire resolution section is disabled. For bitmaps and PNGs the resolution describes how sharp the resulting file will be, and also the amount of disk space that will be required to hold it.

As we hinted above, bitmaps are rather large. This picture will give you some idea of the space required.

For comparison purposes, note that the average novel contains about 3-400,000 bytes of data in the writing, so you can see that picture are truly worth far more than a thousand words. For a bitmap, it makes no difference what the picture has in it; it may be as simple as the above is, or it may be a photograph of a sunset - its size is determined only by the width, height and the color depth, which specifies the number of colors each pixel may display. The following bitmap color depths are generally used:

Each pixel takes up as many bits as described in the table; for example, High COlor take 16 bits (2 bytes) of disk space per pixel. Of course, it's all not as simple as shown in the table; there are other considerations which make, in one case, 8 bit color a lot less cramped than 256 colors might appear to be from the table, but for planning disk files sizes, this is sufficient.

So, the size of a bitmap is equal to the horizontal size (in pixels) times the vertical size times the color depth in bits divided by 8, and the answer is in bytes. The example above of 720 pixels by 480 pixels, at true color (24 bit color depth, 14 million colors) is 1,036,800 bytes long, or roughly one megabyte. PNG graphics compress the bitmap, and so the size will be smaller, though there is no way to predict the exact size of a PNG file until it is actually built. The example above compressed down to 202,640 bytes, almost a five to one compression, but the amount of compression depends greatly on the type of image and how complicated the picture is. In any case, the resolution section displays a filesize that is determined by applying a resolution of two pixels per inch of measured width and height. A box is supplied to modify the displayed Dimensions of the graphic as measured in pixels by raising or lowering an Resolution Adjustment that applies proportionally to both width and height. Two other boxes display the total bitmap size and the world length per pixel on the final graphic. Remember that the size is for a bitmap; a PNG will be something less.

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