在CamanJS中应用数组中的过滤器

Question

I want to store all the filters applied by different buttons and then apply then sequentially on an image. For example, if a user clicks on Brigthness, Noise, Contrast. I want to store these filters and once a user clicks on Apply Filters. I want to apply them all. I tried the following method:

Caman('#canvas', img, function () {
     //this.brightness(10).render();
     var filters = ["brightness(10)", "noise(20)"];
     filters.forEach(function (item, index) {
          this.filters(item);
     });
     this.render();
});

But this gives me the error this.filters is not a function . I can use the commented out line but that will only apply predetermined filters. I want to apply filters based on user selection and I want to apply them all at once when user clicks on apply filters.

Here is a link to the library: http://camanjs.com/examples/

Can anyone please guide me how can I achieve what I want? Let me know if I did not explain the question clearly before downvoting.

Answer 1

That error is showing up because when you use this inside foreach the value of this points the filter array and not caman object Try this

Caman('#canvas', img, function () {
     //this.brightness(10).render();
     var that = this;
     var filters = ["brightness(10)", "noise(20)"];
     filters.forEach(function (item, index) {
        eval('that.'+item); 
     });
     this.render();
});

In above code a copy of this is made which is then passes to inside the loop with name as that

Answer 2

this.filters won't work because 'this' refers to the scope of function(item, index) {...}

I would do something like this:

Caman('#canvas', img, function () {
     // make 'this' available in the scope through 'self' variable
     var self = this;      

     // Filters must hold the function and not a string of the function.
     // so something like:
     var filters = [
       function() { self.brightness(10); },
       function() { self.noise(20); }
     ];

     filters.forEach(function (fn) {
          fn(); // this will execute the anonymous functions in the filters array
     });

     this.render();
});

Answer 3

You can define objects in your array and loop over the effects using forEach() :

Caman('#canvas', img, function () {
  var filters = [
    { name: "brightness", val:10 },
    { name: "noise", val:20 }
  ];
  var that = this;
  filters.forEach(function(effect) {
    that[effect.name](effect.val);
  });
  this.render();
});