mirror of
https://github.com/moparisthebest/kaiwa
synced 2024-11-24 18:22:21 -05:00
115 lines
2.8 KiB
JavaScript
115 lines
2.8 KiB
JavaScript
var Resample = (function (canvas) {
|
|
|
|
// (C) WebReflection Mit Style License
|
|
|
|
// Resample function, accepts an image
|
|
// as url, base64 string, or Image/HTMLImgElement
|
|
// optional width or height, and a callback
|
|
// to invoke on operation complete
|
|
function Resample(img, width, height, onresample) {
|
|
var
|
|
// check the image type
|
|
load = typeof img == "string",
|
|
// Image pointer
|
|
i = load || img
|
|
;
|
|
// if string, a new Image is needed
|
|
if (load) {
|
|
i = new Image;
|
|
// with propers callbacks
|
|
i.onload = onload;
|
|
i.onerror = onerror;
|
|
}
|
|
// easy/cheap way to store info
|
|
i._onresample = onresample;
|
|
i._width = width;
|
|
i._height = height;
|
|
// if string, we trust the onload event
|
|
// otherwise we call onload directly
|
|
// with the image as callback context
|
|
load ? (i.src = img) : onload.call(img);
|
|
}
|
|
|
|
// just in case something goes wrong
|
|
function onerror() {
|
|
throw ("not found: " + this.src);
|
|
}
|
|
|
|
// called when the Image is ready
|
|
function onload() {
|
|
var
|
|
// minifier friendly
|
|
img = this,
|
|
// the desired width, if any
|
|
width = img._width,
|
|
// the desired height, if any
|
|
height = img._height,
|
|
// the callback
|
|
onresample = img._onresample
|
|
;
|
|
// if width and height are both specified
|
|
// the resample uses these pixels
|
|
// if width is specified but not the height
|
|
// the resample respects proportions
|
|
// accordingly with orginal size
|
|
// same is if there is a height, but no width
|
|
width == null && (width = round(img.width * height / img.height));
|
|
height == null && (height = round(img.height * width / img.width));
|
|
// remove (hopefully) stored info
|
|
delete img._onresample;
|
|
delete img._width;
|
|
delete img._height;
|
|
// when we reassign a canvas size
|
|
// this clears automatically
|
|
// the size should be exactly the same
|
|
// of the final image
|
|
// so that toDataURL ctx method
|
|
// will return the whole canvas as png
|
|
// without empty spaces or lines
|
|
canvas.width = width;
|
|
canvas.height = height;
|
|
// drawImage has different overloads
|
|
// in this case we need the following one ...
|
|
context.drawImage(
|
|
// original image
|
|
img,
|
|
// starting x point
|
|
0,
|
|
// starting y point
|
|
0,
|
|
// image width
|
|
img.width,
|
|
// image height
|
|
img.height,
|
|
// destination x point
|
|
0,
|
|
// destination y point
|
|
0,
|
|
// destination width
|
|
width,
|
|
// destination height
|
|
height
|
|
);
|
|
// retrieve the canvas content as
|
|
// base4 encoded PNG image
|
|
// and pass the result to the callback
|
|
onresample(canvas.toDataURL("image/png"));
|
|
}
|
|
|
|
var
|
|
// point one, use every time ...
|
|
context = canvas.getContext("2d"),
|
|
// local scope shortcut
|
|
round = Math.round
|
|
;
|
|
|
|
return Resample;
|
|
|
|
}(
|
|
// lucky us we don't even need to append
|
|
// and render anything on the screen
|
|
// let's keep this DOM node in RAM
|
|
// for all resizes we want
|
|
this.document.createElement("canvas"))
|
|
);
|