Dialog Box: Raster (Bitmap) Files [File Menu]
This dialog can be called from the File menu when either the Spectra window or the Atoms window is active, and the image which goes into the raster file can thus be either the spectrum or the atoms plot.
Windows/Linux only ---------------------
This command can write files in four different formats (File type): Windows device-independent format (.BMP); PC-Paintbrush (.PCX); Tag-image-format (.TIF); or Portable Network Graphics (.PNG).
Macintosh only --------------------
This option writes raster file in the Portable Network Graphics (.PNG) format. Bitmap files can alternatively be written in the PICT File format.
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The drawing may be either black and white or color. If black and white, the pixel size is 1-bit. For color files the pixel size is based on the current screen; 4-bit for standard VGA or other 4-bit display, 8-bit for 256-color display, and 24-bit for 16- or 24-bit display.
The images will look much the same as a screen image, except that for black-and-white files gray shades are always rendered as dot patterns.
If the Compress box is checked, .TIF files are compressed with run-length encoding, which is one of the required formats under the TIFF 6.0 standard. However, some applications may not support this type of compression, or may reject TIF files for other reasons. Also, if the Compress box is checked, 4- and 8-bit BMP files are compressed. 1-bit and 24- bit .BMP files are never compressed. Owing to a system bug, compression of 4-bit .BMP files may not work when banding is used (see below). PCX files are always compressed with their own format. For most purposes, PCX files are the best choice. 24-bit .PCX files can compress well, whereas 24-bit .TIF files are only partially compressed (and then only if there are large areas of black, white or grey), and 24-bit .BMP files are not compressed at all. If applications claim to support .PCX, they will almost surely read files written by VIBRATZ, whereas complete support for .TIF files is less certain.
See Frames for details of the frame and frame units.
Maximum memory. Windows and Mac operating systems both use virtual memory, which means that they pretends that a hard disk can be used in place of actual hardware memory chips. For some applications this is useful, but when writing raster files it often results in "disk thrashing", or constant reading and writing of data to the hard disk.
VIBRATZ is capable of imaging and writing raster files in segments or bands to avoid this problem. This requires repeating the entire drawing process for each band, but this usually is much faster than the reading/writing to disk involved in using virtual memory. To do this requires knowing how much actual chip memory is available. Unfortunately, at present the operating system does not provide this information in a usable form. Thus the user may need to determine this by trial and error using the Maximum memory parameter.
When the Maximum memory parameter is set to zero, VIBRATZ will simply ask the system for a block of memory large enough to image the entire drawing at once. This amount of memory is printed out in the dialog which appears after starting the raster imaging: "nnnn bytes required, mmmm bytes available - will require 1 bands". If this amount of memory is greater than the amount of chip memory available, the system will use virtual memory, which is typically manifested by constant running of the hard disk for long periods. If you change the Maximum memory to some amount smaller than nnnn (say half), VIBRATZ will only request this amount of memory from the system, and virtual memory may not come into play. A Maximum memory Setting should be good for a given session, regardless of the size of the raster file; larger files will use more bands. However, the amount of memory available may depend on whether other applications are active.
The amount of virtual memory is determined by the available space on the hard disk. If this is insufficient, VIBRATZ will automatically use bands, but since virtual memory is being used, it may still be advantageous to use a Maximum memory value which will increase the number of bands.