The image jpeg library

Overview

Package jpeg supplies a .jpeg encoder and decoder. JPEG is defined in ITU-T T.81: https://www.w3.org/Graphics/JPEG/itu-t81.pdf. The image library supplies an Image type and some basic functions to handle it. The color package implements types for representing colors in the usual color models.

Types

Image = clone list

Contains a bitmap, a clone of list in which the elements are the columns of the bitmap, i.e. lists with elements of type Color.

JpegFile = struct (name string, quality int?)

Specifies where we should be loading the .jpg file from, or saving it to, plus the quality of the coding if we are writing the file.

Config = struct (colorModel type, w int, h int)

The metadata for an Image.

Cmyk = struct (c int, m int, y int, k int)

Represents a fully opaque color in the CMYK color model, with 8 bit for each dimension.

Gray = struct (g int)

Represents a shade of gray in 8-bit gray scale.

Rgba = struct (r int, g int, b int, a int)

Represents a color in the RGBA color model, with 8 bits for each dimension.

Rgb = struct (r int, g int, b int)

Like Rgba, but every color is fully opaque.

Rgba_64 = struct (r int, g int, b int, a int)

Represents a color in the RGBA color model, with 16 bits for each dimension.

Rgb_64 = struct (r int, g int, b int)

Like Rgba_64, but every color is fully opaque.

YCbCr = struct (y int, cb int, cr int)

Representation of a fully opaque 24-bit Y'CbCr color, having 8 bits each for one luma and two chroma components.

Color = abstract Cmyk/Gray/Rgb/Rgba/Rgb_64/Rgba_64/YCbCr

The abstract type containing the various color types, Rgb, Rgba, Cmyk, etc.

Commands

get(x ref) from (b JpegFile)

Populates the reference variable with an Image from the file named in the name field of the JpegFile. The quality field is ignored.

post(I Image) to (b JpegFile)

Posts the image to the file named in the name field of the JpegFile. If the quality field is NULL, a default value will be used.

Functions

JpegFile(name string)

Overloads the constructor for JpegFile so that if only the name is supplied, the quality field is NULL.

newImage(w int, h int, fillColor Color)

Constructs a new image of the given dimensions and filled with the given color.

width(I Image) -> int

Returns the width of the image.

height(I Image) -> int

Returns the height of the image.

(I Image) with (args ... pair) -> Image

Overloads the standard with to perform validation.

model(I Image) -> type

Returns the color model of the image, i.e. a type in the abstract type Color.

string(I Image)

Returns the metadata of the image as a string.

swatch(c Color)

Returns a string consisting of "█" with control codes so that it'll display the given color.

Notes

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