kineticjs - createImageRegion for pixels with opacity > 0 not only 1 - opacity

Question

So the createImageRegion method ignores all pixels with a tiny bit of alpha/opacity.
How can you make this function so that also pixels with an opacity of .5 or something will be count for hitdetection?
I looked into KineticJS. A colorKey is added to a hitregion, but it transforms the key to a hex key with no alpha. I can't figure out a way how i could make this work.
Help is much appriciated!
this is where the magic happens. But i don't understand how i can include pixels whith any kind of transpanacy but 0
createImageHitRegion: function (callback) {
var canvas = new Kinetic.Canvas(this.attrs.width, this.attrs.height);
var context = canvas.getContext();
context.drawImage(this.attrs.image, 0, 0);
try {
var imageData = context.getImageData(0, 0, canvas.getWidth(), canvas.getHeight());
var data = imageData.data;
var rgbColorKey = Kinetic.Type._hexToRgb(this.colorKey);
// replace non transparent pixels with color key
for (var i = 0, n = data.length; i < n; i += 4) {
data[i] = rgbColorKey.r;
data[i + 1] = rgbColorKey.g;
data[i + 2] = rgbColorKey.b;
// i+3 is alpha (the fourth element)
}
var that = this;
Kinetic.Type._getImage(imageData, function (imageObj) {
that.imageHitRegion = imageObj;
if (callback) {
callback();
}
});
}
catch (e) {
Kinetic.Global.warn('Unable to create image hit region. ' + e.message);
}
}
When i include: data[i + 3] = 255 (rgbColorKey.a) does not excist, none of the imageevents are working anymore

Answer 1

I found the answer:
for (var i = 0, n = data.length; i < n; i += 4) {
data[i] = rgbColorKey.r;
data[i + 1] = rgbColorKey.g;
data[i + 2] = rgbColorKey.b;
if (!ignoreAlpha && data[i + 3] > 0) {
data[i + 3] = 255;
}
}
This way, every pixel which has a bit of transparancy left, it will get a full color. So if you prototype this to kinetixJS it should work:
Kinetic.Image.prototype.createImageHitRegion = function (callback, ignoreTransparantPixels) {
var canvas = new Kinetic.Canvas(this.attrs.width, this.attrs.height);
var context = canvas.getContext();
var _ignoreTransparantPixels;
if(typeof ignoreTransparantPixels == 'undefined'){
_ignoreTransparantPixels = false;
}
context.drawImage(this.attrs.image, 0, 0);
try {
var imageData = context.getImageData(0, 0, canvas.getWidth(), canvas.getHeight());
var data = imageData.data;
var rgbColorKey = Kinetic.Type._hexToRgb(this.colorKey);
// replace non transparent pixels with color key
for (var i = 0, n = data.length; i < n; i += 4) {
data[i] = rgbColorKey.r;
data[i + 1] = rgbColorKey.g;
data[i + 2] = rgbColorKey.b;
if (!_ignoreTransparantPixels && data[i + 3] > 0) {
data[i + 3] = 255;
}
//trace(data[i + 3]);
// i+3 is alpha (the fourth element)
}
var that = this;
Kinetic.Type._getImage(imageData, function (imageObj) {
that.imageHitRegion = imageObj;
if (callback) {
callback();
}
});
}
catch (e) {
Kinetic.Global.warn('Unable to create image hit region. ' + e.message);
}
}