Editing Grayscale (section)

== Numerical representations ==
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The intensity of a pixel is expressed within a given range between a minimum and a maximum, inclusive. This range is represented in an abstract way as a range from 0 (or 0%) (total absence, black) and 1 (or 100%) (total presence, white), with any fractional values in between. This notation is used in academic papers, but this does not define what "black" or "white" is in terms of [[colorimetry]]. Sometimes the scale is reversed, as in [[printing]] where the numeric intensity denotes how much ink is employed in [[halftoning]], with 0% representing the paper white (no ink) and 100% being a solid black (full ink).

In computing, although the grayscale can be computed through [[rational numbers]], image pixels are usually [[Quantization (signal processing)|quantized]] to store them as unsigned integers, to reduce the required storage and computation. Some early grayscale monitors can only display up to sixteen different shades, which would be stored in [[Binary code|binary]] form using 4 [[bit]]s.{{citation needed|date=March 2022}} But today grayscale images intended for visual display are commonly stored with 8 bits per sampled pixel. This pixel [[Color depth|depth]] allows 256 different intensities (i.e., shades of gray) to be recorded, and also simplifies computation as each pixel sample can be accessed individually as one full [[byte]]. However, if these intensities were spaced equally in proportion to the amount of physical light they represent at that pixel (called a linear encoding or scale), the differences between adjacent dark shades could be quite noticeable as banding [[compression artifact|artifacts]], while many of the lighter shades would be "wasted" by encoding a lot of perceptually-indistinguishable increments. Therefore, the shades are instead typically spread out evenly on a [[gamma correction|gamma-compressed nonlinear scale]], which better approximates uniform perceptual increments for both dark and light shades, usually making these 256 shades enough to avoid noticeable increments.<ref>{{cite book |last= Poynton |first= Charles |date= 2012 |title= Digital Video and HD: Algorithms and Interfaces |edition= 2nd |author-link= Charles Poynton |publisher= [[Morgan Kaufmann]] |url= https://books.google.com/books?id=dSCEGFt47NkC |access-date= 2022-03-31 |pages= 31–35, 65–68, 333, 337 |isbn= 978-0-12-391926-7}}</ref>

Technical uses (e.g. in [[medical imaging]] or [[remote sensing]] applications) often require more levels, to make full use of the [[sensor]] accuracy (typically 10 or 12 bits per sample) and to reduce rounding errors in computations. Sixteen bits per sample (65,536 levels) is often a convenient choice for such uses, as computers manage 16-bit [[Word (data type)|words]] efficiently.  The [[Tagged Image File Format|TIFF]] and [[Portable Network Graphics|PNG]] (among other) [[image file formats]] support 16-bit grayscale natively, although browsers and many imaging programs tend to ignore the low order 8 bits of each pixel. Internally for computation and working storage, image processing software typically uses integer or floating-point numbers of size 16 or 32 bits.