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png-parser

★ 102 Open GitHub ↗

Analyse PNG file format for CTF, python API and CLI

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

![demo](https://raw.githubusercontent.com/Hedroed/png-parser/master/public/screen1.png)

![demo text](https://raw.githubusercontent.com/Hedroed/png-parser/master/public/screen2.png)

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

## Usage
```sh
> $ 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
```sh
python setup.py develop
```

### Run example
```sh
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.

png-parser

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