V-PNG: V PNG Image Processing

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"

---

Todo :

• Handle all types of colors
  • Indexed
  • Grayscale
  • GrayscaleAlpha
  • TrueColor
  • TrueColorAlpha
• Functions to easily manipulate the pixels / image, for example :
  • Resize
  • Mirror
  • Rotate
  • Zoom
  • Slide
  • Crop
  • Invert colors
  • Change colors
  • ...
• Write a png file (Might be hard to have an optimized one)
  • Optimize it
  • Filter pixels lines
  • Group IDAT in chunks
  • Save metadata