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brettcvz/gm-composite.js

Created September 26, 2013 21:31
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  1. brettcvz created this gist Sep 26, 2013.
    49 changes: 49 additions & 0 deletions gm-composite.js
    View file
    Original file line number Diff line number Diff line change
    @@ -0,0 +1,49 @@
    //To use this, in another file call
    //require("./gm-composite.js")(gm.prototype);
    //You can then do gm("baseImage.png").composite(gm("watermark.png"), "SouthEast", function(err, composite_gm_obj){...});

    var gm = require('gm');

    var randInt = function(min, max) {
    return Math.floor(min + (Math.random() * (max-min)));
    };

    var randString = function(len) {
    len = len || 16;

    var chars = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXTZabcdefghiklmnopqrstuvwxyz";
    var ret = "";
    while(ret.length < len) {
    ret += chars[randInt(0, chars.length)];
    }
    return ret;
    };

    module.exports = function(proto) {
    proto.compose = function(other, gravity, callback) {
    // We have potentially two streams to deal with, so we first write the watermark to a file,
    // then pull the base image from stdin and write to stdout
    // gm composite -resize 400x400 -gravity center Watermark.png test_image.png test_output.png
    var path = "/tmp/watermark_"+randString();
    var prev = {
    _subCommand: this._subCommand,
    _out: this._out.slice(), //copy
    _in: this._in.slice()
    };
    var curr = this;
    other.write(path, function(err) {
    curr.subCommand("composite");
    curr.gravity(gravity);
    curr.in(path);

    var composite = gm(curr.stream());

    //re-applying other properties
    composite._subCommand = prev._subCommand;
    composite._out = prev._out;
    composite._in = prev._in;
    callback(null, composite);
    });
    return this;
    };
    };