node-canvas image manipulation

I'm trying to resize and crop an image in node.js

I've been using graphicsmagick:

code is as follows:

gm(path)
.resize(w开发者_如何学运维idth, height)
.crop(50, 50, left, top)
.write(path, function(err){})

It's very simple. I have no idea how to use canvas, what's the equivalent in canvas?

Thanks.

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For some reason, this signature is never used in examples:

context.drawImage(img, sx, sy, sw, sh, dx, dy, dw, dh);

• img = the image element
• sx = source x
• sy = source y
• sw = source width
• sh = source height
• dx = destination x
• dy = destination y
• dw = destination width
• dh = destination height

Crop using sx, sy, sw, sh

Resize using dw, dh