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PNG filename or raw vector containing PNG data

image dimensions

number of colour channels. Integer value in range [1, 4]

number of bits for each colour channel. Either 8 or 16.

PNG image provided as either a file path, or a raw vector containing encoded PNG data

type of R object in which to store image data. Valid types are'array', 'raster', "nativeraster", 'indexed' and 'raw'. Note that indexedimage objects can only be loaded from indexed PNGs.

Should the result be forced into RGBA? Default: FALSEmeans to use the most appropriate format of the given R image type to store the data. IfTRUE, then the image will be forcedinto RGBA color mode.

Flags to apply when reading PNG. Default: 1 (always decode transparency from tRNS chunks). See?spng_decode_flags for other options. Must be an integer.

Default: FALSE. IfTRUE, then transposing the imagefrom row-major (in the PNG), into column-major (in R) will be avoidedif possible. This option only applies when reading grayscale orindexed images. Since the transposition is avoided, the decode step can be faster, but the image will not be in the correct orientation.

'dbl' or 'int'. Default: dbl. When reading PNG into an array,should the data be stored as a double (i.e. real) in the range [0, 1] or an integer in the range [0,255] (for 8 bit images) or [0,65535] (for 16 bit images).

image. Supported image types:

Numeric arrays

Numeric arrays with values in the range [0, 1], with1, 2, 3 or 4 colour planes to represent gray, gray+alpha, rgband rgba pixels, respectively

Rasters

Rasters with a mixture of named colours (e.g. 'red'),and hex colours of the form #RGB, #RGBA, #RRGGBB and #RRGGBBAA

Integer arrays

Integer arrays with values in [0,255] treated as8-bit image data. Integer arrays with values in [0, 65535] treated as16-bit image data

Native rasters

Integer matrices containing colurs in native formati.e. 8-bit RGBA values packed into a single integer

Integer matrix + an indexed palette of colors

Can be saved as an indexed PNG

Raw vectors

Vectors of raw bytes must be accompanied by araw_spec which details how the bytes are to be interpretede.g. colour depth, width and height

If NULL (the default) then return PNG data as raw vector, otherwise writeto the given file path.

character vector of up to 256 colors. If specified, and theimage is a 2D matrix of integer or numeric values, then an indexed PNG is written where the matrix values indicate the colour palettevalue to use. The values in the matrix must range from 0 (for the first colour)

Use PNG filtering to help reduce size? Default: TRUE.If FALSE, then filtering will be disabled which can make image writing faster.

compression level for PNG. Default: -1 meansto use the default compression level. Other validvalues are in range [0, 9]. In general, lower compression levelsresult in faster compression, but larger image sizes. For fastestimage writing, setcompression_levelto 0 to completely disable compression.

Should transposition be avoided if possible so as to maximise the speed of writing the PNG? Default: FALSE. PNG is a row-major image format, but R stores data in column-majorordering. When writing data to PNG, it is often necessary to transposethe R data to match what PNG requires. If this option is set toTRUE then the image is written without this transposition and should speed up PNG creation. This option only has an effectfor 2D integer and numeric matrix formats.

bit depth. default 8. Valid values are 8 and 16. This optiononly has an effect when image to output is a numeric array.

color to be treated as transparentin RGB and Greyscale images - without specifying a full alpha channel. Only a single color can be specified and it will be treated as a fully transparent color in the image. This setting is only used when writing RGB and Greyscale images. For 8-bit RGB images, the valuemay be a hex color value i.e."#RRGGBB" or a vector of 3 numericvalues in the range [0, 255]. For 8-bit greyscale images,must be a single integer value in the range [0, 255].For 16-bit RGB images, the valuemay be a vector of 3 numericvalues in the range [0, 65535]. For 16-bit greyscale images,must be a single integer value in the range [0, 65535].Default: NULL - means to not add a transparency color.

named list of image specifications for encoding a raw vectorto PNG. Useraw_spec() to create such a list in the correct format.This argument is only required if theimage argument is a raw vector.