Fractal Domains 1.3.2 includes the following improvements over version 1.3.1. Most of these features are intended to support the generation of very large images using Fractal Domains. The improvments are:
• More file formats for image export were added (JPEG and uncompressed TIFF).
• Multiple spool files can now be set up to generate images sequentially rather than in parallel.
• Spool files can be set up to automatically export an image after the image is completely generated, and to automatically delete itself after the image is exported.
• A "tiling manager" has been added to allow very large fractals to easily be split up into separate image tiles. A separate spool file is generated for each tile.
• Several bugs have been fixed.
New image file formats
The previous version of Fractal Domains could export fractal images in two formats: PICT and PNG. PICT is the standard Macintosh graphic file format, but it cannot handle images much wider than 4000 pixels. PNG was added in order to allow larger image widths; it also provides much better compression than the PICT format.
Now, two more image file formats have been added: TIFF and JPEG.
TIFF was added for compatibility purposes; it has been around a long time and is a standard file interchange format that can be used with many applications on many platforms. I had always intended to add this format at some point, but I was prompted to include it now because I have received reports that some popular graphics applications may have problems with large images in PNG format (even though Fractal Domains is generating these files correctly). TIFF provides an additional option for users that cannot use the other formats.
Unfortunately, only the uncompressed TIFF format is provided. Currently, the only widely understood compressed TIFF format uses the LZW algorithm, which is patented. (GIF files use the same algorithm, which is one reason why Fractal Domains does not export to that format either.) For this reason, PNG is the preferred format when it can be used (its compression algorithm is superior to comrpessed TIFF, so you get smaller files using that format anyway). Uncompressed TIFF is available as an option in cases where no other format can be used.
JPEG is also supported. Unlike the other three formats, JPEG uses "lossy" compression, which means that some of the original image information is lost. This can cause visible artifacts in certain kinds of images, including some fractal images, so this format should be used with caution. However, for many images JPEG can provide astounding compression ratios with little or no visible effect on the image.
JPEG is a standard format used in web design; all web browsers that can display graphics at all can display JPEG. The high compression ratios with 24 bit color images makes JPEG very popular for displaying fractal images on the web.
I personally have found that often the final step creating a fractal image with Fractal Domains has been to translate the image to JPEG format. Now, this step can be eliminated as the image can be stored directly as JPEG from Fractal Domains.
Since JPEG is lossy, the user may want to use one of the other formats for generating fractals that will be archived or manipulated in some other way. Among the other three formats, PNG provides the best compression and versatility in a lossless format.
There is a "quality" parameter that affects the image quality of JPEG images. This parameter can vary from 1 to 100. Lowering the value of this parameter increases the compression achieved at the cost of image quality. This parameter can be set in the "Preferences" dialog. The default is 95 which is about optimum for high quality images (increasing to 100 makes the file bigger but doesn't substantially increase image quality.) A value of 75 is about as low as you can go without noticeable image degradation in most images.
Serial spool file generation
When creating a spool file, the "Generate Serially" option can be specified. Normally all fractals, whether in spool files or regular fractal edit windows, are generated in parallel. Spool files with the "Generate Serially" option set constitute a special group. Among spool files in this group, only the file in the frontmost window is generated. After the frontmost window is finished, the next-to-front window in the group starts generating, and so on. Other windows that don't have the "Generate Serially" property set still continue generating in parallel.
The order of generation among the "Generate Serially" group can be changed by changing the order of the windows. If another serial window is brought to the front, that window starts generating and the previous front window pauses until the frontmost serial window is finished.
This feature is useful if you want simply want to leave several large images to generate but want to see complete images as soon as possible. However, this feature is most useful in conjunction with the "Auto Image Export" option, discussed in the next section, as it allows multiple large images to be stored to a disk without the necessity of having enough space to store all of the spool files simultaneously.
Automatic image export
It is now possible to set an "Automatic Image Export" option when creating a spool file. This option generates a graphic image file automatically when a spool file is finished generating. Optionally, the spool file can also be deleted after the image file is created.
Since a spool file that is finished generating can't be used for anything other than creating an image file, the deletion option allows you to get rid of the large and unnecessary spool file. This is especially useful when several spool files are being generated using the "Generate Serially" option. If all spool files have the "Generate Serially," "Auto Image Export" and "Delete Spool File after Export" options set, then each spool file is deleted before the next one generates, and no more than one spool file of any size is present on the disk at one time. The disk used only has to be big enought hold one spool file and all of the image files, and as the image files tend to be much smaller than the spool files, this allows the automatic generationg of a greater number of images when the images are very large.
The image file format may be chosen by the user. If the spool files are to be automatically deleted after generation, then it is advised that care be used before choosing JPEG as the file format; in this case it is safer to choose one of the lossless formats as those formats have all of the information contained in the original spool file which wil be deleted.
Of the lossless formats, PICT cannot be used for very large images and TIFF doesn't save as much space over spool files as PNG files do, so for generating several large images using these options the PNG format is usually preferred.
Tiling
The "Tiling..." manager allows a large image to be generated as several separate spool files. The options discussed above can be applied to these spool files. Given an image, the user specifies size of the target image in pixels, the number of tiles in the horizontal and vertical directions, and optionally an overlap value. A spool file for each tile is then created.
Tiling provides the following benefits:
• A very large image can be generated in manageable pieces. If the final image desired is larger than the available printing facilities can handle, it can be constructed from several smaller pieces.
• Parts of a large image can be generated in parallel on separate computers. Once the spool files are created, they can be copied to different machines and opened there where the images will be generated. After all image tiles are generated they can be brought together to construct the final image.
Spool window controls
The header of each spool file window now contains a progress bar showing how much of the image has been generated. To the right of the spool bar is a triangle that can be clicked to reveal controls for several spool file options.
These controls allow you to see whether the serial and auto export options have been set for the spool file, which is especially useful for spool files that have been interrupted and resumed. You can also change these options at any time during generation of the image. You should be aware that any such changes will only be in effect during the current session; if you close the spool file window and reopen it later, the options will revert to the value they had when the spool file was created.
Bug fixes
The following bugs have been found in Fractal Domains since the 1.3.1 release.
1) Using the Julia tool on Newton and Halley type fractals doesn't work. Creating Julia sets of these types directly works OK, but if you turn off the Julia flag and then use the Julia tool subsequently to create a new Newton or Halley Julia fractal, the resulting fractal is not of the correct type and a crash can even result.
This has been fixed in 1.3.2.
2) The "Windows" menu sometimes loses track of open windows. When this happens it doesn't recover until you restart the program.
At first I didn't know what circumstances caused this, but eventually I found it only happened when Fractal Domains was launched by opening a file from the Finder.
This has been fixed in 1.3.2.
Known bugs
When generating critical points for use in placing orbit traps, some "spurious" critical points that don't correspond to real critical points of the function can be generated for some Newton and Halley type fractals.
I noticed this when trying to reproduce a particular fractal as a Rational fractal. The spurious critical points actual caused some interesting and attractive artifacts to occur in the image, so I don't want to just eliminate this bug outright. Probably, I will add the capability to specify arbitrary points to be added to the list of orbit trap origins (I was planning to do this eventually anyway) and then I will be able to fix this without destroying existing fractals, as I can then just add the spurious roots to the list.
This change has not yet been made in 1.3.2; be aware this kind of thing can happen.
