Glossary of "Portable Network Graphics (PNG) Specification (Second Edition)"

Term entries in the "Portable Network Graphics (PNG) Specification (Second Edition)" glossary

W3C Glossaries

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PNG image

From Portable Network Graphics (PNG) Specification (Second Edition) (2003-11-10)

result of transformations applied by a PNG encoder to a reference image , in preparation for encoding as a PNG datastream , and the result of decoding a PNG datastream.

PNG signature

From Portable Network Graphics (PNG) Specification (Second Edition) (2003-11-10)

sequence of bytes appearing at the start of every PNG datastream . It differentiates a PNG datastream from other types of datastream and allows early detection of some transmission errors.

reduced image

From Portable Network Graphics (PNG) Specification (Second Edition) (2003-11-10)

pass of the interlaced PNG image extracted from the PNG image by pass extraction .

reference image

From Portable Network Graphics (PNG) Specification (Second Edition) (2003-11-10)

rectangular array of rectangular pixels , each having the same number of samples , either three (red, green, blue) or four (red, green, blue, alpha ). Every reference image can be represented exactly by a PNG datastream and every PNG datastream can be converted into a reference image. Each channel has a sample depth in the range 1 to 16. All samples in the same channel have the same sample depth. Different channels may have different sample depths.

RGB merging

From Portable Network Graphics (PNG) Specification (Second Edition) (2003-11-10)

converting an image in which the red, green, and blue samples for each pixel have the same value, and the same sample depth , into an image with a single greyscale channel .

sample

From Portable Network Graphics (PNG) Specification (Second Edition) (2003-11-10)

intersection of a channel and a pixel in an image.

number of bits used to represent a sample value. In an indexed-colourPNG image, samples are stored in the palette and thus the sample depth is always 8 by definition of the palette. In other types of PNG image it is the same as the bit depth.

mapping of a range of sample values onto the full range of a sample depth allowed in a PNG image.

sample depth

From Portable Network Graphics (PNG) Specification (Second Edition) (2003-11-10)

number of bits used to represent a sample value. In an indexed-colourPNG image, samples are stored in the palette and thus the sample depth is always 8 by definition of the palette. In other types of PNG image it is the same as the bit depth.

mapping of a range of sample values onto the full range of a sample depth allowed in a PNG image.

sample depth scaling

From Portable Network Graphics (PNG) Specification (Second Edition) (2003-11-10)

mapping of a range of sample values onto the full range of a sample depth allowed in a PNG image .

scanline

From Portable Network Graphics (PNG) Specification (Second Edition) (2003-11-10)

row of pixels within an image or interlaced PNG image .

source image

From Portable Network Graphics (PNG) Specification (Second Edition) (2003-11-10)

image which is presented to a PNG encoder .

truecolour

From Portable Network Graphics (PNG) Specification (Second Edition) (2003-11-10)

image representation in which each pixel is defined by samples , representing red, green, and blue intensities and optionally an alpha sample (in which case it is referred to as truecolour with alpha).

white point

From Portable Network Graphics (PNG) Specification (Second Edition) (2003-11-10)

chromaticity of a computer display's nominal white value.

zlib

From Portable Network Graphics (PNG) Specification (Second Edition) (2003-11-10)

particular format for data that have been compressed using deflate -style compression. Also the name of a library containing a sample implementation of this method. The format is defined in [RFC-1950] .

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