V-PNG: V PNG Image Processing

October 28, 2021 · View on GitHub

How to use :

Its simple, download the module and then you just have to do :

import vpng

png_file := vpng.read("image.png") or { return }
png_file.write("output.png")

Tips

To deal with the different kinds of Pixel, (cf: Pixel Types) the prefered method is :

pixel := png_file.pixels[i]
match pixel {
    vpng.Grayscale {
        ...
    }
    vpng.TrueColor {
        ...
    }
    ...
    ...
}

Methods

Method	use
`read(filename string) ?PngFile`	Parses the given `filename` png file and returns an optional `PngFile`.
`(PngFile).write(filename string)`	Writes the given `PngFile` in the `filename` png file.

Types

Structure

PngFile, Object returned by the .parse function. Contains all useful information about the parsed png file :

pub struct PngFile {
    ihdr       IHDR
pub:
    width      int          // Width of image
    height     int          // Height of image
    pixel_type PixelType    // Pixels type
pub mut:
    pixels     []Pixel      // Modifiable pixel array
}

Pixel Types

PixelType, Enum for type of pixel possible in the PngFile :

pub enum PixelType {
    indexed
    grayscale
    grayscalealpha
    truecolor
    truecoloralpha
}

PixelType, Generic type for the different possible types of pixels :

pub type Pixel = Grayscale | GrayscaleAlpha | Indexed |     TrueColor | TrueColorAlpha

Pixels :

Indexed (Not supported yet) :

pub struct Indexed {
pub mut:
    index byte
}

Grayscale (Not supported yet) :

pub struct Grayscale {
pub mut:
    gray byte
}

GrayscaleAlpha (Not supported yet) :

pub struct GrayscaleAlpha {
pub mut:
    gray  byte
    alpha byte
}

TrueColor (RGB) :

pub struct TrueColor {
pub mut:
    red   byte
    green byte
    blue  byte
}

TrueColorAlpha (RGBA) :

pub struct TrueColorAlpha {
pub mut:
    red   byte
    green byte
    blue  byte
    alpha byte
}

Examples:

png-printer.v: Give it a .png file and it will print it for you in the terminal.
redline.v: Give it an input .png file and an output .png file. It will read the input, add a diagonal red line and write the result on the output file.

How to compile them from GitHub repository:

[vpng]$ v examples/png-printer.v -path "..|@vlib|@vmodules"