lodepng.Common

Types and functions common to both the encode and decoder of lodepng, as well as image format conversion routines

License:
Copyright (c) 2005-2007 Lode Vandevenne All rights reserved.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

- Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
- Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.
- Neither the name of Lode Vandevenne nor the names of his contributors may be used to endorse or promote products derived from this software without specific prior written permission.


THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

Authors:
Lode Vandevenne (original version in C++), Lutger Blijdestijn (D version) : lutger dot blijdestijn at gmail dot com, Stewart Gordon (modifications)

Date:
August 7, 2007

References:
Original lodepng
PNG Specification
PNG Suite: set of test images
OptiPNG: tool to experimentally optimize png images

class PngException : object.Exception;
Png specific exception.

Instead of errors codes, this port of lodepng makes use of exceptions. At the moment, the decoder is very strict and will tolerate no errors whatsoever even if they could safely be ignored. CRC checking is always done. This might be slightly relaxed in a future release to be more in line with the recommendations of the specification.

enum ColorType ;
An enumeration of the color types supported by the png format.

see the png specification for details.

Greyscale
allowed bit depths: 1, 2, 4, 8 and 16

RGB
allowed bit depths: 8 and 16

Palette
allowed bit depths: 1, 2, 4 and 8

GreyscaleAlpha
allowed bit depths: 8 and 16

RGBA
allowed bit depths: 8 and 16

Any
one of the above

ubyte[] convert (ubyte[] source, ref PngInfo info, ColorType destColorType = cast(ColorType)cast(ubyte)6u);
ubyte[] convert (ubyte[] source, PngInfo info, ref ubyte[] buffer, ColorType destColorType = cast(ColorType)cast(ubyte)6u);
Convert source pixels from the color type described by info the color type destColorType.

Conversion can be from any color type supported by the png specification to 24 / 32 bit RGB(A). If RGBA is specified and the info has a colorkey, transparency is applied.

If a buffer is given, it may be used to store the result and a slice from it can be returned.

Returns:
converted image in RGB(A) format, pixels are from left to right, top to bottom

struct PngImage ;
Description of the image.

static PngImage opCall (uint w, uint h, ubyte bd, ColorType ct, ubyte ilace = cast(ubyte)0);
constructor

uint width ;
in pixels

uint height ;
in pixels

ubyte bitDepth ;
bits per color channel, see also: ColorType

ubyte bpp ;
bits per pixel

ColorType colorType ;
the color format, see also: ColorType

struct PngInfo ;
Png file and image description.

A simple data type describing the png file. Usually the image field will contain all the required information.

There is one member that behaves a bit different: parseText(bool). This is used to tell the decoder whether to ignore textual metadata (which it does by default).

PngImage image ;
Information related to the image , see also: PngImage.

ubyte[] backgroundColor ;
Recommended background color or empty if none is given.

Interpretation of the array depends on the color type:

palette
palette[ backgroundColor [0]] is the background color
greyscale (8 bit or less)
backgroundColor [0] is used
RGB(A) (8 bit or less)
backgroundColor [0..3] is the rgb triplet used
16-bit greyscale or RGB(A)
same as above, but the color/greyscale channels are 2 bytes wide




ubyte[4u][] palette ;
Palette colors or empty if this image does not make use of it.

Each palette entry is a 32-bit RGBA pixel represented as an ubyte[4]. When a colorkey is specified, it is automatically applied to the palette by the decoder.



bool colorKey ;
Whether there is a colorkey transparency associated with the png image.

Note that this is applicable only when the image has no seperate alpha channel, and the image format is not ColorType.Palette. In the latter case, transparency is always stored in the palette by the decoder. The transparent color is stored in keyR, keyG and keyB, for brevity greyscale is in keyR.

ushort keyR ;


ushort keyG ;


ushort keyB ;


void parseText (bool flag);
By default, lodepng will not parse textual metadata, set to true if this is desired.

bool parseText ();
Whether parsing of metadata is enabled.

PngText text ();
Retrieve the dictionary of textual metadata.

When no text is read, because it was set to be ignored or there wasn't any, this returns null so check the return value.

In the case that a PngInfo instance is passed more than once to the api, an existing dictionary is not reused. Instead a new one will be created. It is therefore not necessary to copy anything, the strings they are all yours.



bool hasUnicodeText ();
Returns whether any unicode text has been stored.

bool hasLatin1Text ();
Returns whether any latin-1 text has been stored.

class PngText ;
Dictionary of key-value textual metadata in utf-8 and / or latin-1 encoding.

this();


this(char[][char[]] unicodeText);


this(ubyte[][ubyte[]] latin1Text);


int opApply (int delegate(ref char[] keyword, ref char[] contents) dg);
Visit utf-8 dictionary

int opApply (int delegate(ref ubyte[] keyword, ref ubyte[] contents) dg);
Visit latin-1 dictionary

PngText opIndexAssign (ubyte[] value, ubyte[] keyword);
PngText opIndexAssign (char[] value, char[] keyword);
Assign key-value pair

uint numChannels (ColorType colorType);
Number of color or alpha channels associated with this color type.

bool isGreyscale (ColorType colorType);


bool hasAlphaChannel (ColorType colorType);


bool hasAlpha (ref PngInfo info);
Whether the image contains any alpha information (channel / colorkey / palette)

struct Chunk ;
Abstracts a png chunk

static Chunk fromStream (ubyte[] byteStream);
Construct a Chunk from a stream of bytes

Params:
ubyte[] byteStream the whole chunk needs to be available in this array

Returns:
a crc-checked chunk from byteStream, the data is sliced, not copied

uint length ();
Returns:
total length of this chunk (not only data)

Chunk dup ();
Returns:
chunk containing a copy of the data

uint type ;
type of the chunk packed into a uint, see the png specification for details

ubyte[] data ;
(slice of) the data of this chunk

uint toUint (ubyte a, ubyte b, ubyte c, ubyte d);
Params:
ubyte a
ubyte b
ubyte c
ubyte d

Returns:


uint toUint (ubyte[] source);
Params:
ubyte[] source

Returns:


const uint IHDR ;


const uint IDAT ;


const uint PLTE ;


const uint tRNS ;


const uint bKGD ;


const uint IEND ;


const uint tEXt ;


const uint iTXt ;


const uint zTXt ;


const uint cHRM ;


const uint gAMA ;


const uint hIST ;


const uint iCCP ;


const uint oFFs ;


const uint pCAL ;


const uint pHYs ;


const uint sBIT ;


const uint sCAL ;


const uint sPLT ;


const uint sRGB ;


char[] chunkTypeToString (uint chunkType);
Params:
uint chunkType

Returns:


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