lodepng.Encode

• conformant encoding of 24-bit RGB and 32-bit RGBA PNG images
• automatic conversion of other color formats
• setting the compression and filter methods
• textual key-value metadata: normal and compressed latin1, unicode (utf-8)
• transparency / colorkey
• encoding raw chunks
• the following chunks are written by the encoder
  • IHDR (image information)
  • IDAT (pixel data)
  • IEND (the final chunk)
  • tRNS (colorkey)
  • bKGD (suggested background color)
  • tEXt (uncompressed latin-1 key-value strings)
  • zTXt (compressed latin-1 key-value strings)
  • iTXt (utf8 key-value strings)

• Ouput in any color formats other than 24-bit RGB or 32-bit RGBA
• Interlacing
• The encoder does not understand the following chunk types:
  • PLTE (color palette)
  • cHRM (device independent color info)
  • gAMA (device independent color info)
  • iCCP (device independent color info)
  • sBIT (original number of significant bits)
  • sRGB (device independent color info)
  • pHYs (physical pixel dimensions)
  • sPLT (suggested reduced palette)
  • tIME (last image modification time)

ubyte[] encode (ubyte[] source, PngInfo info);

Encode pixels as a png file

This function will attempt to convert to 24-bit RGB if it is a lossless operation, otherwise the resulting image will be in the 32-bit RGBA format. The array returned can be written to disk as a png file.

Params:

ubyte[] source	the pixels to be encoded
PngInfo info	description of the source pixels

Throws:
PngException

Returns:
png file of the raw pixels provided by source and described by settings.info

ubyte[] encode (ubyte[] source, PngInfo info, ref Chunk [] chunkList);

Encode pixels and / or raw chunks as a png file

If chunkList contains IDAT chunks, they must be in order and no source pixels should be provided

Params:

ubyte[] source	the pixels to be encoded, can be null
PngInfo info	description of the source pixels
Chunk [] chunkList	array of chunks to be written

Throws:
PngException

Returns:
png file of the raw pixels provided by source and described by info

ubyte[] encode (ubyte[] source, Settings options);

Encode pixels as a png file

See Also:
Settings

Params:

ubyte[] source	the pixels to be encoded
Settings options	description and options needed to encode the png file

Throws:
PngException

Returns:
png file of the raw pixels provided by source and described by options.info

ubyte[] encode (ubyte[] source, Settings options, ref Chunk [] chunkList);

Encode pixels as a png file

See Also:
Settings

Params:

ubyte[] source	the pixels to be encoded
Settings options	description and options needed to encode the png file
Chunk [] chunkList	array of chunks to be written

Throws:
PngException

Returns:
png file of the raw pixels provided by source and described by options.info

enum FilterStrategy ;

Filter method

The png specification defines five types of filters. In addition each scanline can have a different filtering method applied (Dynamic). The latter method usually gives the best compression, when a fixed method is preferred paeth gives the best result most of the times.

None

Up

Sub

Average

Paeth

Dynamic

enum CompressionStrategy ;

Zlib compression method

Which compression scheme works best depends on the type of image. Tools such as optipng can figure this out experimentally. However, RLE seems to give the best results in compression and performance.

Default

Filtered

RLE

None

struct Settings ;

Controls all information needed to encode a png file

static Settings opCall ();
static Settings opCall (PngInfo info, bool autoRemoveAlpha = false);
static Settings opCall (PngImage image, bool autoRemoveAlpha = false);

constructor

PngInfo info ;

png image information

ColorType targetColorType ;

The colortype of the target image

lodepng can only encode in RGB(A) format (yet?)

. If the format is set ColorType.Any, RGB or RGBA is chosen depending on whether the source image has an alpha channel.

bool autoRemoveAlpha ;

Remove alpha channel

If set to true and the source image has an alpha channel, this will be removed if (and only if) the image is fully opaque or a colorkey can be written. This is considered a lossless operation.

bool compressText ;

if zlib compression is to be used on text

ubyte compressionLevel ;

zlib compression level, affects memory use. Must be in range 0-9

FilterStrategy filterStrategy ;

see FilterStrategy

CompressionStrategy compressionStrategy ;

see CompressionStrategy