...get a form of anti-aliasing applied to your image -P.N.L.
I've sometimes calculated fractal images 4 times larger in X and Y and downsized them. This may be a bit of overkill, but I feel like this provides the ultimate in image quality of a Fractint fractal that you can reasonably do. I only use 4 times 'over-sizing' and 'quarter down-sizing' for creating desktop wallpaper from .GIF fractals. It's important to have the output from the resizing be a JPG image -- and make sure the JPG encoding 'quality' setting is high enough to not discard some of the smoothing that you have just gained by the re-sizing... Also, make sure that the re-sizing algorithm used actually combines pixels -- there are a few apps that just discard unused pixels and output a smaller percentage of your original pixels when downsizing images! Some apps let you set the re-sizing algorithm: - Don't use 'Nearest Neighbor'! - Bicubic is fine (& a typical default) and better than Bilinear - Even better (but only by a small amount) than Bicubic is Lanczos The reason you need JPG output is as follows: Consider a re-sizing algorithm reducing an image in size by 1/2. When the algorithm needs to combine an white input pixel with an black input pixel (for example) to write out a single pixel of a particular shade of gray, the needed gray is highly likely to *not* be in the 256 colors in the GIF color map. (Unless the entire image is all shades of gray.) This problem is true for all pairs of colors that the re-sizing algorithm needs to combine. The JPG pixel color encoding algorithm can create and write out the exact needed color to best smooth your image. --------------------- A closely related issue that can inadvertently degrade images is poor monitor gamma adjustment. Unfortunately, your fractal can be correctly anti-aliased, but degraded during viewing on your monitor. --------------------- A quick look at the Wikipedia article: http://en.wikipedia.org/wiki/Anti-aliased on anti-aliasing can give a feeling for what is going on at the pixel level. Especially see Figure 3 in the article. Wikipedia says: "In digital signal processing, anti-aliasing is the technique of minimizing the distortion artifacts known as aliasing when representing a high-resolution signal at a lower resolution. [This is what is being done when we calculate a finite resolution fractal image using an 'infinite resolution' fractal formula. -hhl] Anti-aliasing is used in digital photography, computer graphics, digital audio, and many other applications. Anti-aliasing means removing signal components that have a higher frequency than is able to be properly resolved by the recording (or sampling) device. This removal is done before (re)sampling at a lower resolution. When sampling is performed without removing this part of the signal, it [can] cause undesirable artifacts such as the black-and-white noise near the top of figure 1-a below." Note that these artifacts are only generated by particular patterns in an image. In practice, many of the fractals created by Fractint do not have these patterns and thus, do not suffer from the artifacts when re-sizing is used to approximate true anti-aliasing. ------------------------ A quick look at the Wikipedia article: http://en.wikipedia.org/wiki/Gamma_correction on monitor gamma is useful if you're not familiar with this. The article's pictures show what a strong influence gamma has on the displayed image. Wikipedia says: "...image files are almost always stored on computers and communicated across the Internet with gamma encoding. ...still image files ([such] as JPEG) are explicitly encoded (that is, they carry gamma-encoded values, not linear intensities), as are motion picture files (such as MPEG)." - Hal Lane ######################### (\__/) # hallane@earthlink.net # (='.'=) ######################### (")_(") -----Original Message----- From: fractint-bounces+hallane=earthlink.net@mailman.xmission.com On Behalf Of JackOfTradeZ@comcast.net Sent: Wednesday, March 31, 2010 12:43 PM To: fractint@mailman.xmission.com Subject: Re: [Fractint] whatever """I assume you know that you can render to disk at even larger sizes, then use a graphic editor like IrfanView to resize/resample down to half the original, so as to get a form of anti-aliasing applied to your image. It makes the edges even smoother, and usually ends up adding additional colors from the basic 256 (8 BitsPerPixel) mode to the 16.7 million (24 BitsPerPixel) mode.""" Why do I always find out about these things so late in life ........ ? .