Small JS library to watermarks pictures using JS and HTML5 Canvas element.
This library is primary intended for back-end usage, allowing the backend users to add watermarks / badges to the images in a non-removable way (the watermarks are rendered over the image itself). In front-end there are several ways of simulate a watermark over an image without the need of using this library.
JQuery 1.5+
Web browser with HTML5 Canvas support (IE9+)
my_watermarked = new Watermark(); // Create new object instance
my_watermarked
.setPicture('img/source-image.jpg') // Base picture, url or data-url
.addWatermark('img/wm-1.png') // Url or data-url
.render( function(){
// Do something when watermarking ends
});If you get a message in the brower's console about «A "tainted" canvas», you are trying to use images with the CORS enabled read a brief explanation at MDN.
If you are going to work with uploaded images stored in a different server domain, you will need to enable CORS configuration in the third-party storage, in order to let the library work with images. For example, if you are using Amazon S3 storage for your images, this is the CORS documentation.
The watermarking proccess is asyncronous, so if you want to access / use the resulting watermarked images you must do it inside the .render() method, passing a callback function that will be executed once the watermarking is finished.
You can pass an optional array of widths to the .setPicture() method to create several sizes from the original base image, this eases the task of creating several sizes of the watermarked image automatically.
my_watermarked
.setPicture('img/source-image.jpg', [640, 320, 240]) // Array of thumbs widths
//...The watermark images can have several optional settings
.addWatermark('img/wm-3.png', // Image url or data-url
{
position: [1,1], // Default is [0.5, 0.5]
scale: 2.0, // Default is 1.0
opacity: 0.5 // Default is 1.0
}
)position indicates the position of the watermark relative to the base image, first component of the array is the horizontal position, and second one the vertical position, both in a range of [0-1]:
// Positions
// left top -> [0, 0]
// left center -> [0, 0.5]
// left bottom -> [0, 1]
// right top -> [1, 0]
// right center -> [1, 0.5]
// right bottom -> [1, 1]
// center top -> [0.5, 0]
// center center -> [0.5, 0.5]
// center bottom -> [0.5, 1]scale sets an enlargement / reduction to the watermark. So if you want the watermark be half the size the original image you must set this value 0.5. Remember that enlarging images can produce blurry results.
You have two methods to retrieve the resulting watermarked images, both return an array of elements:
my_watermarked.getImgs( format, quality ); // Returns array of <img>s
my_watermarked.getDataUrls( format, quality ); // Returns array of data-urls
// format: 'image/png' (default) / 'image/jpeg'
// quality: float in range [ 0-1 ] ( 1 is best quality )Sample usage:
// Gets all the resulting images in PNG format
var resulting_imgs = my_watermarked.getImgs( 'image/png' );
// Add all of them to the <body> element
$.each( resulting_imgs, function(idx, item) {
$('body').append( $(item) );
});
// Get all the resulting data urls in Jpeg 90% quality
var resulting_data_urls = my_watermarked.getDataUrls( 'image/jpeg', 0.9 );
console.log(resulting_data_urls);Clear watermark configurations and results in case you want to make a new fresh watermark.
.clearWatermarks();As both .setPicture() and .addWatermark() accept a data-url image as parameter you can build complex / dynamic watermarks passing a functión that return data-url as result. Take a look to the procedural-watermark-sample.js included in the repo to see the sample function that creates the price badge .
Following the demo code, with all the avaliable options.
my_watermarked = new Watermark();
my_watermarked
.setPicture('img/source-image.jpg', [400, 250])
.addWatermark('img/wm-1.png',
{
position: [0,0]
}
)
.addWatermark('img/wm-2.png')
.addWatermark('img/wm-3.png',
{
position: [1,1],
scale: 2.0,
opacity: 0.5
}
)
.addWatermark(
proceduralWatermark( 'DESDE', '99', ',99€'),
{
position: [1,0]
}
)
.render( function(){
// var resulting_canvas = wm.getCanvases();
// $.each( resulting_canvas, function(idx, item) {
// $('body').append( $(item) );
// });
var resulting_imgs = my_watermarked.getImgs( 'image/png' );
$.each( resulting_imgs, function(idx, item) {
$('body').append( $(item) );
});
var resulting_data_urls = my_watermarked.getDataUrls( 'image/jpeg', 0.9 );
console.log(resulting_data_urls);
}); // render callback // Return the data-URL of image in selector
my_watermarked.getDataUrlFromImg( $('selector') );- 0.2 Avoid web browser cache issues when requesting CORS images
- 0.1 Initial release
- Add vertical constraints to the thumbnails widths
- Add a
fitWidthto the watermark options...