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add down scale function for thumb (better quality) #1

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add down scale function for thumb (better quality) #1

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41 changes: 40 additions & 1 deletion image-resizer.js
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Original file line number Diff line number Diff line change
Expand Up @@ -32,6 +32,45 @@ IR.ImageResizer = (function() {

return canvas.toDataURL();
};

var thumb = function(image, maxWidth, maxHeight) {

var cwidth = 0;
var cheight = 0;
// set the correct accepted dimensions on the canvas
if (image.width > image.height) {
if (image.width > maxWidth) {
cheight = image.height * maxWidth / image.width; // maintain aspect ratio
cwidth = maxWidth;
}
} else {
if (image.height > maxHeight) {
cwidth = image.width * maxHeight / image.height;
cheight = maxHeight;
}
}

// Step it down several times
var can2 = document.createElement('canvas');
can2.width = cwidth*8;
can2.height = cheight*8;
var ctx2 = can2.getContext('2d');

// Draw it at 1/2 size 3 times (step down three times)

ctx2.drawImage(img, 0, 0, cwidth*4, cheight*4);
ctx2.drawImage(can2, 0, 0, cwidth*4, cheight*4, 0, 0, cwidth*2, cheight*2);
ctx2.drawImage(can2, 0, 0, cwidth*2, cheight*2, 0, 0, cwidth, cheight);


var can = document.getElementById('canvas1');
can.width = cwidth;
can.height = cheight;
var ctx = can.getContext('2d');
ctx.drawImage(can2, 0, 0, cwidth, cheight, 0, 0, cwidth, cheight);

return can.toDataURL();
};

/*
* Converts a data URI object to a Blob object
Expand All @@ -55,4 +94,4 @@ IR.ImageResizer = (function() {
toBlob: toBlob
};

})();
})();