Vue-pattern-placeholder

This plugin provides a placeholder component for Vue.js. It uses canvas to render patterns from input string like URL.

Table of contents

• Demo
• Sample images
• Installation
• • Usage
• • API
• Warning
• Inspiration
• TODO
• Acknowledgements

Demo

Sample images

Recent updates

• 2019-05-04 Import format changed, refer to usage section.

Installation

To install this plugin, open terminal in your Vue project directory and type:

npm i --save-dev vue-pattern-placeholder

This command will install the plugin in your project node_modules dir and add it as a project development dependency in project's package.json file.

If you need this plugin as a generic dependency, type this command instead:

npm i --save-dev vue-pattern-placeholder

Usage

To import a component, write:

import patternPlaceholder from 'vue-pattern-placeholder'

Add it to the components property

components: {
    patternPlaceholder
},

Now you can use it in your template:

<patternPlaceholder
  :width="150" :height="150"
  :input="''+item_data.media_id"
  label="150x150"
  label_style="900 30px Arial" label_color="#000"
  :hue_range="[70, 170]"
  :lightness_range="[0, 100]"
/>

I recommend to start playing with hue_range and lightness_range properties to reach the best look.

API

For now, none of the parameters are required.

Option	Data-type(s)	Description	Default
width	Number	width of an image	250
height	Number	height of an image	250
input	String	this text will be converted to a pattern	Hi there! :-)
label	String	text label to show	No label
label_style	String	canvas font style. Example: 900 30px Arial	20px Helvetica bold
label_color	String	color of a label. Example: #777	#777
metric	String	metric, used to create a pattern. Examples: Euclidean, Manhattan, Minkovski	Manhattan
debug	Boolean	allows to show center points for a Voronoi pattern	false
hue_range	Array	sets a color range in degrees. Example: [0, 359]	[0, 359]
lightness_range	Array	lightness range for pattern pieces in percents. Example: [0, 100]	[0, 100]

Warning

Please be aware that this project is still in a testing stage. Use at your own risk. Ideas and bug reports are welcome.

Inspiration

I thought about converting text to an image and I remembered Voronoi patterns: these are easy to implement and look very nice.

Then I had an idea:

• take a string, process it using a SHA-256 hash function
• extract hash bytes
• use pairs of bytes, converting each to a float value between 0 and 1 to place X and Y points
• count pattern segments, use numbers to set each one's hue in HSV color palette
• calculate pattern areas
• use areas to determine lightness of a pattern segment in HSV

TODO

• Overlay text
• Fix wrong color representation in overlay text
• Autoreload fix (probably needs a destructor)
• Fix empty canvas on width / height change
• Fixed beforeDestroy bug
• Added demo
• Consider integrating label style and color into one parameter
• Label style settings in key-value format
• Extend hue setting to a list of several possible hues

Acknowledgements

Thanks to AnatolV from RosettaCode for a nice Voronoi diagram implementation.

Thanks to emn178 for js-sha256 library. It is easy to use and helps a lot.