Dithering for laser Image Lightburn vs Imag-r comparison how to and outcome Photo Engraving / Etch
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2:09 Lightburn Edit
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Dither is an intentionally applied form of noise used to randomize quantization error, preventing large-scale patterns such as color banding in images. Dither is routinely used in processing of both digital audio and video data, and is often one of the last stages of mastering audio to a CD.
A common use of dither is converting a grayscale image to black and white, such that the density of black dots in the new image approximates the average gray level in the original.
Algorithms
There are several algorithms designed to perform dithering. One of the earliest, and still one of the most popular, is the Floyd–Steinberg dithering algorithm, which was developed in 1975. One of the strengths of this algorithm is that it minimizes visual artifacts through an error-diffusion process; error-diffusion algorithms typically produce images that more closely represent the original than simpler dithering algorithms.[17]
Dithering methods include:
Thresholding (also average dithering[18]): each pixel value is compared against a fixed threshold. This may be the simplest dithering algorithm there is, but it results in immense loss of detail and contouring.[17]
Random dithering was the first attempt (at least as early as 1951) to remedy the drawbacks of thresholding. Each pixel value is compared against a random threshold, resulting in a staticky image. Although this method doesn't generate patterned artifacts, the noise tends to swamp the detail of the image. It is analogous to the practice of mezzotinting.[17]
Patterning dithers using a fixed pattern. For each of the input values, a fixed pattern is placed in the output image. The biggest disadvantage of this technique is that the output image is larger (by a factor of the fixed pattern size) than the input pattern.[17]
Ordered dithering dithers using a dither matrix. For every pixel in the image, the value of the pattern at the corresponding location is used as a threshold. Neighboring pixels do not affect each other, making this form of dithering suitable for use in animations. Different patterns can generate completely different dithering effects. Though simple to implement, this dithering algorithm is not easily changed to work with free-form, arbitrary palettes.
A halftone dithering matrix produces a look similar to that of halftone screening in newspapers. This is a form of clustered dithering, in that dots tend to cluster together. This can help hide the adverse effects of blurry pixels found on some older output devices. The primary use for this method is in offset printing and laser printers. In both these devices, the ink or toner prefers to clump together and will not form the isolated dots generated by the other dithering methods.
A Bayer matrix[17] produces a very distinctive cross-hatch pattern.
A matrix tuned for blue noise, such as those generated by the void-and-cluster method,[19] produces a look closer to that of an error diffusion dither method.