pixel-editor/js/_changeZoom.js

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JavaScript
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/** Changes the zoom level of the canvas
* @param {*} direction 'in' or 'out'
* @param {*} cursorLocation The position of the cursor when the user zoomed
*/
function changeZoom (direction, cursorLocation) {
// Computing current width and height
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var oldWidth = canvasSize[0] * zoom;
var oldHeight = canvasSize[1] * zoom;
var newWidth, newHeight;
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//change zoom level
//if you want to zoom out, and the zoom isnt already at the smallest level
if (direction == 'out' && zoom > 1) {
zoom -= Math.ceil(zoom / 10);
newWidth = canvasSize[0] * zoom;
newHeight = canvasSize[1] * zoom;
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//adjust canvas position
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layers[0].setCanvasOffset(
layers[0].canvas.offsetLeft + (oldWidth - newWidth) * cursorLocation[0]/oldWidth,
layers[0].canvas.offsetTop + (oldHeight - newHeight) * cursorLocation[1]/oldWidth);
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}
//if you want to zoom in
else if (direction == 'in' && zoom + Math.ceil(zoom/10) < window.innerHeight/4){
zoom += Math.ceil(zoom/10);
newWidth = canvasSize[0] * zoom;
newHeight = canvasSize[1] * zoom;
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//adjust canvas position
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layers[0].setCanvasOffset(
layers[0].canvas.offsetLeft - Math.round((newWidth - oldWidth)*cursorLocation[0]/oldWidth),
layers[0].canvas.offsetTop - Math.round((newHeight - oldHeight)*cursorLocation[1]/oldHeight));
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}
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//resize canvas
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layers[0].resize();
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// adjust brush size
currentTool.updateCursor();
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}