png-parser

Best tool to analyse PNG files, it shows you PNG chunks : header, palette, and text.

pip install --user git+https://github.com/Hedroed/png-parser

Usage

> $ png-parser --help

 ▄▄▄· ▐ ▄  ▄▄ •  ▄▄▄· ▄▄▄· ▄▄▄  .▄▄ · ▄▄▄ .▄▄▄
▐█ ▄█•█▌▐█▐█ ▀ ▪▐█ ▄█▐█ ▀█ ▀▄ █·▐█ ▀. ▀▄.▀·▀▄ █·
 ██▀·▐█▐▐▌▄█ ▀█▄ ██▀·▄█▀▀█ ▐▀▀▄ ▄▀▀▀█▄▐▀▀▪▄▐▀▀▄
▐█▪·•██▐█▌▐█▄▪▐█▐█▪·•▐█ ▪▐▌▐█•█▌▐█▄▪▐█▐█▄▄▌▐█•█▌
.▀   ▀▀ █▪·▀▀▀▀ .▀    ▀  ▀ .▀  ▀ ▀▀▀▀  ▀▀▀ .▀  ▀
v2.0.0

usage: png-parser [-h] [-a | -c CHUNK_ID | -t TYPE | --text] [-d] [--length] [--crc] [--hex] [--show] [--output OUTPUT] [-v] file

Prints PNG text sections

positional arguments:
  file                  A PNG image

optional arguments:
  -h, --help            Show this help message and exit
  -a, --all             Print all chunk infos
  -c CHUNK_ID, --chunk CHUNK_ID
                        Select chunk with this id
  -t TYPE, --type TYPE  Select chunk by type
  --text                Display all text chunk
  -d, --data            Print chunk data
  --length              Print chunk length
  --crc                 Print chunk crc and check if it is right
  --hex                 Print bytes position in Hexadecimal
  -s, --show            Show image
  --output OUTPUT       Save image (fix input file errors if any)
  -v, --verbose         Increase verbosity

API

Class PngParser

PngParser(file)

file: str or file type

PngParser.get_image_data()

PngParser.set_image_data()

PngParser.get_chunk_by_index(idx)

PngParser.get_chunk_by_type(type)

Class Chunk

Chunk(type, data=None, crc=None)

Chunk.update_crc()

Chunk.length

Class ImageData

ImageData(header, data, palette=None)

ImageData.scanlines

ImageData.get_pixel(x, y)

ImageData.set_pixel(x, y, pixel) ImageData.set_pixel(x, y, data)

Class Scanline

Scanline(filter, data, previous=None)

Scanline.filter

Scanline.data

Class Pixel

Pixel(type, channels) Pixel.getitem

Dev

Install for development

python setup.py develop

Run example

python example/read_png_filters.py

DOC

PNG Chunks

Length	Chunk type	Chunk data	CRC
4 bytes	4 bytes	Length bytes	4 bytes

Critical Chunks:

• IHDR : must be the first chunk; it contains (in this order) the image's width, height, bit depth, color type, compression method, filter method, and interlace method (13 data bytes total).

• PLTE : contains the palette; list of colors.

• IDAT : contains the image, which may be split among multiple IDAT chunks. Such splitting increases filesize slightly, but makes it possible to generate a PNG in a streaming manner. The IDAT chunk contains the actual image data, which is the output stream of the compression algorithm.

• IEND : marks the image end.

Ancillary Chunks:

• bKGD : gives the default background color. It is intended for use when there is no better choice available, such as in standalone image viewers (but not web browsers; see below for more details).

• cHRM : gives the chromaticity coordinates of the display primaries and white point.

• dSIG : is for storing digital signatures.

• eXIf : stores Exif data.

• gAMA : specifies gamma.

• hIST : can store the histogram, or total amount of each color in the image.

• iCCP : is an ICC color profile.

• iTXt : contains a keyword and UTF-8 text, with encodings for possible compression and translations marked with language tag. The Extensible Metadata Platform (XMP) uses this chunk with a keyword 'XML:com.adobe.xmp'

• pHYs : holds the intended pixel size and/or aspect ratio of the image.

• sBIT : (significant bits) indicates the color-accuracy of the source data.

• sPLT : suggests a palette to use if the full range of colors is unavailable.

• sRGB : indicates that the standard sRGB color space is used.

• sTER : stereo-image indicator chunk for stereoscopic images.[15]

• tEXt : can store text that can be represented in ISO/IEC 8859-1, with one key-value pair for each chunk. The "key" must be between 1 and 79 characters long. Separator is a null character. The "value" can be any length, including zero up to the maximum permissible chunk size minus the length of the keyword and separator. Neither "key" nor "value" can contain null character. Leading or trailing spaces are also disallowed.

• tIME : stores the time that the image was last changed.

• tRNS : contains transparency information. For indexed images, it stores alpha channel values for one or more palette entries. For truecolor and grayscale images, it stores a single pixel value that is to be regarded as fully transparent.

• zTXt : contains compressed text (and a compression method marker) with the same limits as tEXt.

(c) https://en.wikipedia.org/wiki/Portable_Network_Graphics#File_header