lodepng.Decode

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.

About:
The decoder is small but sufficient for most purposes. It is compliant to the png specification and has been tested with the png suite. The api is procedural and simple, meant to be easily integrated. It is compatible with the Phobos and Tango libraries. For Tango, lodepng expects the zlib binding from phobos in etc.c.zlib.d
This module publicly imports lodepng.Common, where you'll find the data types used by both the encoder and decoder, as well as some utility and image format conversion routines.

Date:
August 7, 2007

Features:
The following features are supported by the decoder:
  • conformant decoding of PNGs (all color types, bit depth, interlace mode, CRC checking, etc.)
  • support for translucent PNG's, including translucent palettes and color key
  • textual key-value meta-data
  • the following chunks are interpreted by the decoder
    • IHDR (image information)
    • PLTE (color palette)
    • IDAT (pixel data)
    • IEND (the final chunk)
    • tRNS (transparency for palettized images)
    • bKGD (suggested background color)
    • tEXt (uncompressed latin-1 key-value strings)
    • zTXt (compressed latin-1 key-value strings)
    • iTXt (utf8 key-value strings)


Limitations:
The following features are not supported.
  • editing a PNG image (unless you use the decoder, then edit it, then use the encoder, but ignored chunks will then be gone from the original image)
  • Streaming / progressive display. All data must be available and is processed in one call.
  • The following optional chunk types are not interpreted by the decoder
    • 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)


Examples:
Here is an example how you could use LodePNG with opengl, see the api documentation for details. 
uint loadPNG(char[] filename)
{
    uint textureID;

    glEnable(GL_TEXTURE_2D);
    glGenTextures(1, &textureID);
    glBindTexture(GL_TEXTURE_2D, textureID);
    glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR);

    PngInfo info;
    ubyte[] image = decode32(cast(ubyte[])std.file.read(filename), info);

    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, info.image.width, info.image.height, 0, GL_RGBA, GL_UNSIGNED_BYTE,
                        image.ptr);
    return textureID;
}


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

PngImage readHeader (ubyte[] source);
PngImage readHeader (ubyte[] source, out ubyte interlace);
Parse png image header from memory. The first 33 bytes of the png file need to be available

Throws:
PngException

ubyte[] decode (ubyte[] source, ref PngInfo info, ubyte[] buffer = null);
Decode source png file

If a buffer is provided, it may be used to store the result. See bufferSize for details.

Throws:
PngException

Returns:
Decoded image pixels. The color format of the resulting image is the same as the source image, see lodepng.Common.convert and decode32 if a specific color format is desired.

ubyte[] decode32 (ubyte[] source, ref PngInfo info, ubyte[] buffer = null);
Decode source png file to RGBA format

Throws:
PngException

Returns:
decoded image pixels in 32-bit RGBA format

uint bufferSize (ref PngImage image);
Predict size of buffer needed for decoding

Estimate of the amount of heap memory needed to decode an image. Interlaced images, images with a color format of less than 8 bits per pixel and the parsing of certain information such as text will allocate more heap memory.

Page was generated with on Tue Aug 7 19:26:37 2007