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62-432: The original MegaPixel Display released in 1990 was a monochrome 17" monitor displaying four brightness levels (black, dark gray, light gray, and white) in a fixed resolution of 1120 × 832 at 92 DPI (just shy of a true megapixel at 931,840 total pixels) at 68 Hz. It integrated a mono microphone , mono speaker , stereo RCA sockets , a 3.5 mm headphone socket and a socket for the keyboard (which in turn provided

124-490: A 12-point font was represented with 12 pixels on a Macintosh, and 16 pixels (or a physical display height of maybe 19 ⁄ 72 inch) on a Windows platform at the same zoom, and so on. The negative consequence of this standard is that with 96 PPI displays, there is no longer a one-to-one relationship between the font size in pixels and the printout size in points. This difference is accentuated on more recent displays that feature higher pixel densities . This has been less of

186-532: A DPI aware flag (manifest) as "true" inside the EXE. Windows 8.1 retains a per-application option to disable DPI virtualization of an app. Windows 8.1 also adds the ability for different displays to use independent DPI scaling factors, although it calculates this automatically for each display and turns on DPI virtualization for all monitors at any scaling level. Windows 10 adds manual control over DPI scaling for individual monitors. There are some ongoing efforts to abandon

248-417: A PPI ( pixels per inch ) value, which is to be used when printing the image. This number lets the printer or software know the intended size of the image, or in the case of scanned images , the size of the original scanned object. For example, a bitmap image may measure 1,000 × 1,000 pixels, a resolution of 1 megapixel . If it is labelled as 250 PPI, that is an instruction to the printer to print it at

310-528: A default of 96 PPI. These default specifications arose out of the problems rendering standard fonts in the early display systems of the 1980s, including the IBM -based CGA , EGA , VGA and 8514 displays as well as the Macintosh displays featured in the 128K computer and its successors. The choice of 72 PPI by Macintosh for their displays arose from existing convention: the official 72 points per inch mirrored

372-502: A dimly lit encoding (creation) environment with an ambient correlated color temperature (CCT) of 5003 K. This differs from the CCT of the illuminant ( D65 ). Using D50 for both would have made the white point of most photographic paper appear excessively blue. The other parameters, such as the luminance level, are representative of a typical CRT monitor. For optimal results, the ICC recommends using

434-509: A higher bit depth to maintain a low color error rate (∆E). An ICC profile or a lookup table may be used to convert sRGB to other color spaces. ICC profiles for sRGB are widely distributed, and the ICC distributes several variants of sRGB profiles, including variants for ICCmax, version 4, and version 2. Version 4 is generally recommended, but version 2 is still commonly used and is the most compatible with other software including browsers. Version 2 of

496-429: A line within the span of 1 inch (2.54 cm). Similarly, dots per centimetre ( d/cm or dpcm ) refers to the number of individual dots that can be placed within a line of 1 centimetre (0.394 in). DPI is used to describe the resolution number of dots per inch in a digital print and the printing resolution of a hard copy print dot gain, which is the increase in the size of the halftone dots during printing. This

558-685: A manifest file or using an API. For programs that do not declare themselves as DPI-aware, Windows Vista supports a compatibility feature called DPI virtualization so system metrics and UI elements are presented to applications as if they are running at 96 DPI and the Desktop Window Manager then scales the resulting application window to match the DPI setting. Windows Vista retains the Windows XP style scaling option which when enabled turns off DPI virtualization for all applications globally. DPI virtualization

620-527: A matrix to obtain CIE XYZ (the matrix has infinite precision, any change in its values or adding non-zeroes is not allowed): This is actually the matrix for BT.709 primaries, not just for sRGB, the second row corresponds to the BT.709-2 luma coefficients (BT.709-1 had a typo in these coefficients). The CIE XYZ values must be scaled so that the Y of D65 ("white") is 1.0 ( X = 0.9505, Y = 1.0000, Z = 1.0890). This

682-464: A new PPI for the file. For vector images , since the file is resolution independent, there is no need to resample the image before resizing it as it prints equally well at all sizes. However, there is still a target printing size. Some image formats, such as Photoshop format, can contain both bitmap and vector data in the same file. Adjusting the PPI in a Photoshop file will change the intended printing size of

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744-437: A problem with the advent of vector graphics and fonts being used in place of bitmap graphics and fonts. Moreover, many Windows software programs have been written since the 1980s which assume that the screen provides 96 PPI. Accordingly, these programs do not display properly at common alternative resolutions such as 72 PPI or 120 PPI. The solution has been to introduce two concepts: Software programs render images to

806-437: A relatively low resolution, typically in the range of 60 to 90 DPI (420 to 280 μm). An inkjet printer sprays ink through tiny nozzles, and is typically capable of 300–720 DPI. A laser printer applies toner through a controlled electrostatic charge, and may be in the range of 600 to 2,400 DPI. The DPI measurement of a printer often needs to be considerably higher than the pixels per inch (PPI) measurement of

868-427: A size of 4 × 4 inches. Changing the PPI to 100 in an image editing program would tell the printer to print it at a size of 10 × 10 inches. However, changing the PPI value would not change the size of the image in pixels which would still be 1,000 × 1,000. An image may also be resampled to change the number of pixels and therefore the size or resolution of the image, but this is quite different from simply setting

930-430: A small discontinuity in the curve. Some authors adopted these incorrect values, in part because the draft paper was freely available and the official IEC standard is behind a paywall. For the standard, the rounded value of Φ was kept and X was recomputed as 0.04045 to make the curve continuous, resulting in a slope discontinuity from 1/12.92 below the intersection to 1/12.70 above. The sRGB specification assumes

992-467: A socket for the mouse). A unique feature was that the monitor was connected to the computer by a single 6 foot cable which provided power, video signals and the aforementioned signals. A severe problem with this setup was that the monitor could not be switched off completely while the computer was powered on. The screen could be switched black but the cathode heater always remained on. This led to extreme screen dimming after some years of use, especially when

1054-443: A straight-line section that leads to zero. In practice, there is still debate and confusion around whether sRGB data should be displayed with pure 2.2 gamma as defined in the standard, or with the inverse of the OETF. Some display manufacturers and calibrators use the former, while some use the latter. When a power law γ 2.2 {\displaystyle \gamma ^{2.2}}

1116-527: A video display in order to produce similar-quality output. This is due to the limited range of colours for each dot typically available on a printer. At each dot position, the simplest type of color printer can either print no dot, or print a dot consisting of a fixed volume of ink in each of four color channels (typically CMYK with cyan , magenta , yellow and black ink) or 2 = 16 colours on laser, wax and most inkjet printers, of which only 14 or 15 (or as few as 8 or 9) may be actually discernible depending on

1178-506: A wider gamut. Such images used on the Internet may be converted to sRGB using color management tools that are usually included with software that works in these other color spaces. The two dominant programming interfaces for 3D graphics, OpenGL and Direct3D , have both incorporated support for the sRGB gamma curve. OpenGL supports textures with sRGB gamma encoded color components (first introduced with EXT_texture_sRGB extension, added to

1240-498: Is a compatibility option as application developers are all expected to update their apps to support high DPI without relying on DPI virtualization. Windows Vista also introduces Windows Presentation Foundation . WPF .NET applications are vector-based, not pixel-based and are designed to be resolution-independent. Developers using the old GDI API and Windows Forms on .NET Framework runtime need to update their apps to be DPI aware and flag their applications as DPI-aware. Windows 7 adds

1302-480: Is caused by the spreading of ink on the surface of the media. Up to a point, printers with higher DPI produce clearer and more detailed output. A printer does not necessarily have a single DPI measurement; it is dependent on print mode, which is usually influenced by driver settings. The range of DPI supported by a printer is most dependent on the print head technology it uses. A dot matrix printer , for example, applies ink via tiny rods striking an ink ribbon, and has

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1364-434: Is mapped to -384 ⁄ 510 ... 639 ⁄ 510 , and bg-sYCC using the same number of bits for a range of approximately -0.75–1.25 for Y; -1–1 for C. As this conversion can result in sRGB values outside the range 0–1, the amendment describes how to apply the gamma correction to negative values, by applying − f (− x ) when x is negative (and f is the sRGB↔linear functions described above). This

1426-506: Is the color triangle defined by these primaries, which are set such that the range of colors inside the triangle is well within the range of colors visible to a human with normal trichromatic vision. As with any RGB color space , for non-negative values of R, G, and B it is not possible to represent colors outside this triangle. The primaries come from HDTV ( ITU-R BT.709 ), which are somewhat different from those for older color TV systems ( ITU-R BT.601 ). These values were chosen to reflect

1488-573: Is used to display data that was intended to be displayed on displays that use the piecewise function, the result is that the shadow details will be "crushed" towards hard black. A straight line that passes through (0,0) is y = x Φ {\displaystyle y={\frac {x}{\Phi }}} , and a gamma curve that passes through (1,1) is y = ( x + A 1 + A ) Γ {\displaystyle y=\left({\frac {x+A}{1+A}}\right)^{\Gamma }} If these are joined at

1550-481: Is usually true but some color spaces use 100 or other values (such as in CIELAB , when using specified white points). The first step in the calculation of sRGB from CIE XYZ is a linear transformation, which may be carried out by a matrix multiplication. (The numerical values below match those in the official sRGB specification, which corrected small rounding errors in the original publication by sRGB's creators, and assume

1612-617: The World Wide Web . It was subsequently standardized by the International Electrotechnical Commission (IEC) as IEC 61966-2-1:1999. sRGB is the current defined standard colorspace for the web, and it is usually the assumed colorspace for images that are neither tagged for a colorspace nor have an embedded color profile . sRGB essentially codifies the display specifications for the computer monitors in use at that time, which greatly aided its acceptance. sRGB uses

1674-407: The default (or only available) working color space. However, consumer-level CCDs are typically uncalibrated, meaning that even though the image is being labeled as sRGB, one can not conclude that the image is color-accurate sRGB. If the color space of an image is unknown and it is an 8 bit image format, sRGB is usually the assumed default, in part because color spaces with a larger gamut need

1736-441: The 0 to 1 range. This clipping can be done before or after the gamma calculation, or done as part of converting to 8 bits. If values in the range 0 to 255 are required, e.g. for video display or 8-bit graphics, the usual technique is to multiply by 255 and round to an integer. Due to the standardization of sRGB on the Internet, on computers, and on printers, many low- to medium-end consumer digital cameras and scanners use sRGB as

1798-546: The 2° standard colorimetric observer for CIE XYZ. ) This matrix depends on the bitdepth. These linear RGB values are not the final result; gamma correction must still be applied. The following formula transforms the linear values into sRGB: where C {\displaystyle C} is R {\displaystyle R} , G {\displaystyle G} , or B {\displaystyle B} . These gamma-compressed values (sometimes called "non-linear values") are usually clipped to

1860-411: The 72 pixels per inch that appeared on their display screens. ( Points are a physical unit of measure in typography , dating from the days of printing presses , where 1 point by the modern definition is 1 ⁄ 72 of the international inch (25.4 mm), which therefore makes 1 point approximately 0.0139 in or 352.8 μm). Thus, the 72 pixels per inch seen on the display had exactly

1922-595: The DPI Image resolution unit in favour of a metric unit , giving the inter-dot spacing in dots per centimetre (px/cm or dpcm), as used in CSS3 media queries or micrometres (μm) between dots. A resolution of 72 DPI, for example, equals a resolution of about 28 dpcm or an inter-dot spacing of about 353 μm. SRGB sRGB is a standard RGB (red, green, blue) color space that HP and Microsoft created cooperatively in 1996 to use on monitors, printers, and

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1984-414: The ICC profile specification does not officially support piecewise parametric curve encoding ("para"), though version 2 does support simple power-law functions. Nevertheless, lookup tables are more commonly used as they are computationally more efficient. Even when parametric curves are used, software will often reduce to a run-time lookup table for efficient processing. As the sRGB gamut meets or exceeds

2046-608: The NeXT Sound Box . The cost for the 17" MegaPixel Color Display was US$ 2,995 (equivalent to $ 6,700 in 2023), with the MegaPixel Display costing US$ 995 (equivalent to $ 2,230 in 2023). From the NeXT User's Reference: Dots per inch Dots per inch ( DPI , or dpi ) is a measure of spatial printing , video or image scanner dot density, in particular the number of individual dots that can be placed in

2108-528: The Windows XP era. High DPI displays became mainstream around the time Windows 8 was released. Display scaling by entering a custom DPI irrespective of the display resolution has been a feature of Microsoft Windows since Windows 95. Windows XP introduced the GDI+ library which allows resolution-independent text scaling. Windows Vista introduced support for programs to declare themselves to the OS that they are high-DPI aware via

2170-461: The ability to change the DPI by doing only a log off, not a full reboot and makes it a per-user setting. Additionally, Windows 7 reads the monitor DPI from the EDID and automatically sets the system DPI value to match the monitor's physical pixel density, unless the effective resolution is less than 1024 × 768. In Windows 8 , only the DPI scaling percentage is shown in the DPI changing dialog and

2232-469: The approximate color of consumer CRT phosphors at the time of its design. Since flat-panel displays at the time were generally designed to emulate CRT characteristics, the values also reflected prevailing practice for other display devices as well. The reference display characterisation is based on the characterisation in CIE 122. The reference display is characterised by a nominal power-law gamma of 2.2, which

2294-441: The bitmap portion of the data and also change the intended printing size of the vector data to match. This way the vector and bitmap data maintain a consistent size relationship when the target printing size is changed. Text stored as outline fonts in bitmap image formats is handled in the same way. Other formats, such as PDF, are primarily vector formats that can contain images, potentially at a mixture of resolutions. In these formats

2356-403: The computer was not turned off overnight as in a server setup or in a busy software lab. This problem was later rectified with the now ultra rare 4000 A model rated at 10,000 hours (~14 months). The display has a stand that allows it to be tilted. The stand also features two rollers that can be used to move the monitor back and forth despite its heavy weight. The stand also provides a place for

2418-449: The conversion of linear light or signal intensity to a gamma-compressed image data. It is a piecewise compound function and has an approximate γ {\displaystyle \gamma } of 2.2, with a linear portion near zero to avoid an infinite slope which emphasizes signal (camera) noise. Near zero, a γ 1 / 2.4 {\displaystyle \gamma ^{1/2.4}} power law curve intercepts

2480-578: The core in OpenGL 2.1) and rendering into sRGB gamma encoded framebuffers (first introduced with EXT_framebuffer_sRGB extension, added to the core in OpenGL 3.0). Correct mipmapping and interpolation of sRGB gamma textures has direct hardware support in texturing units of most modern GPUs (for example nVidia GeForce 8 performs conversion from 8-bit texture to linear values before interpolating those values), and does not have any performance penalty. Amendment 1 to IEC 61966-2-1:1999, approved in 2003, includes

2542-456: The definition of a Y′Cb′Cr′ color representation called sYCC . Although the RGB color primaries are based on BT.709, the equations for transformation from sRGB to sYCC and vice versa are based on BT.601 . sYCC uses 8 bits for the components resulting in a range of approximately 0–1 for Y; -0.5–0.5 for C. The amendment also contains a 10-bit-or-more encoding called bg-sRGB where 0–1

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2604-486: The display of the raw DPI value has been removed. In Windows 8.1 , the global setting to disable DPI virtualization (only use XP-style scaling) is removed and a per-app setting added for the user to disable DPI virtualization from the Compatibility tab. When the DPI scaling setting is set to be higher than 120 PPI (125%), DPI virtualization is enabled for all applications unless the application opts out of it by specifying

2666-403: The display screen, particularly the lowercase characters. Furthermore, there was the consideration that computer screens are typically viewed (at a desk) at a distance 30% greater than printed materials, causing a mismatch between the perceived sizes seen on the computer screen and those on the printouts. Microsoft tried to solve both problems with a hack that has had long-term consequences for

2728-448: The encoding viewing environment (i.e., dim, diffuse lighting) rather than the less-stringent typical viewing environment. The sRGB component values R s r g b {\displaystyle R_{\mathrm {srgb} }} , G s r g b {\displaystyle G_{\mathrm {srgb} }} , B s r g b {\displaystyle B_{\mathrm {srgb} }} are in

2790-554: The gamut of a low-end inkjet printer , an sRGB image is often regarded as satisfactory for home printing. sRGB is sometimes avoided by high-end print publishing professionals because its color gamut is not big enough, especially in the blue-green colors, to include all the colors that can be reproduced in CMYK printing. Images intended for professional printing via a fully color-managed workflow (e.g. prepress output) sometimes use another color space such as Adobe RGB (1998) , which accommodates

2852-705: The image. As such, 600 dpi (sometimes 720) is now the typical output resolution of entry-level laser printers and some utility inkjet printers, with 1,200–1,440 and 2,400–2,880 being common "high" resolutions. This contrasts with the 300–360 (or 240) dpi of early models, and the approximate 200 dpi of dot-matrix printers and fax machines, which gave faxed and computer-printed documents—especially those that made heavy use of graphics or coloured block text—a characteristic "digitized" appearance, because of their coarse, obvious dither patterns, inaccurate colours, loss of clarity in photographs, and jagged ("aliased") edges on some text and line art. In printing, DPI (dots per inch) refers to

2914-576: The keyboard when not in use, freeing up the (real) desktop in front. When the NeXTstation Color and the NeXTdimension board were released, NeXT sold rebranded color monitors (e.g. Sony Trinitron ) with 13W3 connectors as MegaPixel Color Display in either 17" or 21". Remaining connections (formerly built into the MegaPixel Display) were provided via a DB-19 Y-cable to a separate box,

2976-407: The norm. This dithered printing process could require a region of four to six dots (measured across each side) to accurately reproduce the color in a single pixel. An image that is 100 pixels wide may need to be 400 to 600 dots in width in the printed output; if a 100 × 100-pixel image is to be printed in a one-inch square, the printer must be capable of 400 to 600 dots per inch to reproduce

3038-436: The number of colours is still typically less than on a monitor. Most printers must therefore produce additional colours through a halftone or dithering process, and rely on their base resolution being high enough to "fool" the human observer's eye into perceiving a patch of a single smooth colour. The exception to this rule is dye-sublimation printers , which can apply a much more variable amount of dye—close to or exceeding

3100-421: The number of the 256 levels per channel available on a typical monitor—to each "pixel" on the page without dithering, but with other limitations: These disadvantages mean that, despite their marked superiority in producing good photographic and non-linear diagrammatic output, dye-sublimation printers remain niche products, and thus other devices using higher resolution, lower color depth, and dither patterns remain

3162-427: The output resolution of a printer or imagesetter, and PPI (pixels per inch) refers to the input resolution of a photograph or image. DPI refers to the physical dot density of an image when it is reproduced as a real physical entity, for example printed onto paper. A digitally stored image has no inherent physical dimensions, measured in inches or centimetres. Some digital file formats record a DPI value, or more commonly

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3224-549: The point ( X , X /Φ) then: To avoid a kink where the two segments meet, the derivatives must be equal at this point: We now have two equations. If we take the two unknowns to be X and Φ then we can solve to give The values A = 0.055 and Γ = 2.4 were chosen so the curve closely resembled the gamma-2.2 curve. This gives X ≈ 0.0392857, Φ ≈ 12.9232102 . These values, rounded to X = 0.03928, Φ = 12.92321 sometimes describe sRGB conversion. Draft publications by sRGB's creators further rounded Φ = 12.92 , resulting in

3286-534: The range 0 to 1. When represented digitally as 8-bit numbers, these color component values are in the range of 0 to 255, and should be divided (in a floating point representation) by 255 to convert to the range of 0 to 1. where C {\displaystyle C} is R {\displaystyle R} , G {\displaystyle G} , or B {\displaystyle B} . These gamma-expanded values (sometimes called "linear values" or "linear-light values") are multiplied by

3348-437: The rest of the world, it is 210 mm × 297 mm – called A4 . B5 is 176 mm × 250 mm). A consequence of Apple's decision was that the widely used 10-point fonts from the typewriter era had to be allotted 10 display pixels in em height, and 5 display pixels in x-height . This is technically described as 10 pixels per em ( PPEm ). This made 10-point fonts be rendered crudely and made them difficult to read on

3410-466: The sRGB working group determined was representative of the CRTs used with Windows operating systems at the time. The ability to directly display sRGB images on a CRT without any lookup greatly helped sRGB's adoption. Gamma also usefully encodes more data near the black, which reduces visible noise and quantization artifacts. The standard also defines a opto-electronic transfer function (OETF), which defines

3472-466: The same color primaries and white point as ITU-R BT.709 standard for HDTV , a transfer function (or gamma ) compatible with the era's CRT displays , and a viewing environment designed to match typical home and office viewing conditions. sRGB defines the chromaticities of the red, green, and blue primaries , the colors where one of the three channels is nonzero and the other two are zero. The gamut of chromaticities that can be represented in sRGB

3534-598: The same physical dimensions as the 72 points per inch later seen on a printout, with 1 pt in printed text equal to 1 px on the display screen. As it is, the Macintosh 128K featured a screen measuring 512 pixels in width by 342 pixels in height, and this corresponded to the width of standard office paper (512 px ÷ 72 px/in ≈ 7.1 in, with a 0.7 in margin down each side when assuming 8 + 1 ⁄ 2  in × 11 in North American paper size ; in

3596-594: The strength of the black component, the strategy used for overlaying and combining it with the other colours, and whether it is in "color" mode. Higher-end inkjet printers can offer 5, 6 or 7 ink colours giving 32, 64 or 128 possible tones per dot location (and again, it can be that not all combinations will produce a unique result). Contrast this to a standard sRGB monitor where each pixel produces 256 intensities of light in each of three channels ( RGB ). While some color printers can produce variable drop volumes at each dot position, and may use additional ink-color channels,

3658-489: The target PPI of the bitmaps is adjusted to match when the target print size of the file is changed. This is the converse of how it works in a primarily bitmap format like Photoshop , but has exactly the same result of maintaining the relationship between the vector and bitmap portions of the data. Since the 1980s, Macs have set the default display "DPI" to 72 PPI, while the Microsoft Windows operating system has used

3720-425: The understanding of what DPI and PPI mean. Microsoft began writing its software to treat the screen as though it provided a PPI characteristic that is 4 ⁄ 3 of what the screen actually displayed. Because most screens at the time provided around 72 PPI, Microsoft essentially wrote its software to assume that every screen provides 96 PPI (because 72 × 4 ⁄ 3 = 96). The short-term gain of this trickery

3782-496: The virtual screen and then the operating system renders the virtual screen onto the physical screen. With a logical PPI of 96 PPI, older programs can still run properly regardless of the actual physical PPI of the display screen, although they may exhibit some visual distortion thanks to the effective 133.3% pixel zoom level (requiring either that every third pixel be doubled in width/height, or heavy-handed smoothing be employed). Displays with high pixel densities were not common up to

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3844-503: Was twofold: Thus, for example, a 10-point font on a Macintosh (at 72 PPI) was represented with 10 pixels (i.e., 10 PPEm), whereas a 10-point font on a Windows platform (at 96 PPI) at the same zoom level is represented with 13 pixels (i.e., Microsoft rounded 13 + 1 ⁄ 3 to 13 pixels, or 13 PPEm) – and, on a typical consumer grade monitor, would have physically appeared around 15 ⁄ 72 to 16 ⁄ 72 inch high instead of 10 ⁄ 72 . Likewise,

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