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Processing.js for Processing Devs: Difference between revisions
Processing.js for Processing Devs (view source)
Revision as of 01:03, 25 October 2010
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# To use it, download Processing.js here: http://processingjs.org/download | # To use it, download Processing.js here: http://processingjs.org/download | ||
# Make your Processing *.pde files as you normally would, for example hello-web.pde | # Make your Processing *.pde files as you normally would, for example hello-web.pde | ||
# Create a web page that includes Processing.js as well as a <canvas> with info about where to get your sketch file: | # Create a web page that includes Processing.js as well as a <canvas> with info about where to get your sketch file (you can specify multiple *.pde files, separating them with spaces, and can name them anything, foo.pjs or foo.pde, or foo.js): | ||
<pre> | <pre> | ||
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==1. Writing a Processing.js Sketch== | ==1. Writing a Processing.js Sketch== | ||
There's nothing you should do differently | There's nothing you should do differently to write sketches for Processing.js: you write your Processing.js code exactly like Processing. For most people, this will mean using the Processing IDE, which has the nice benefit of letting you write, run, and test your code all in once place. Remember, any valid Processing sketch should also be a valid Processing.js sketch. | ||
If you want to experiment with web-based Processing.js code editors, you can also try these: | If you want to experiment with web-based Processing.js code editors, you can also try these: | ||
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stroke(255); | stroke(255); | ||
ellipse(50, 50, 25, 25); | ellipse(50, 50, 25, 25); | ||
println( | println("hello web!"); | ||
} | } | ||
</pre> | </pre> | ||
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* processing-0.9.7.min.js | * processing-0.9.7.min.js | ||
The version numbers may be different as you read this, but note the file extensions. Both end in .js, but one also has .min. The .min version is | The version numbers may be different as you read this, but note the file extensions. Both end in .js, but one also has .min. The .min version is Processing.js in a minified form, which means it will be smaller to download (minified JavaScript uses tricks like removing whitespace and renaming long variable names to single letters). File sizes, and download times, matter on the web in a way they don't with normal Processing sketches. | ||
==3. Creating a Processing.js Web Page== | ==3. Creating a Processing.js Web Page== | ||
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</pre> | </pre> | ||
That's it! No <html> or <body> tags, no title, no CSS, just the processing.js script, and a canvas. While there isn't much here, it's important to understand what is. First, the script tag has a src attribute, which is the file to load. This could be a full url or a relative path. In this case the browser is going to look for a file named '''processing-0.9.7.min.js''' in the same directory as your web page. | That's it! No <html> or <body> tags, no title, no CSS, just the processing.js script, and a canvas. While there isn't much here, it's important to understand what is. First, the script tag has a '''src''' attribute, which is the file to load. This could be a full url or a relative path. In this case the browser is going to look for a file named '''processing-0.9.7.min.js''' in the same directory as your web page. | ||
The second thing in this web page is a canvas tag. Notice that it too has an attribute, '''data-processing-sources'''. This is a list of filenames (or just one filename if you only have 1 file) separated by spaces (filenames and URLs on the web can't include spaces, so space is a safe choice for separating lists). In this case, the browser is going to look for a file named '''hello-web.pde''' located in the same directory as your page page. | The second thing in this web page is a <canvas> tag. Notice that it too has an attribute, '''data-processing-sources'''. This is a list of filenames (or just one filename if you only have 1 file) separated by spaces (filenames and URLs on the web can't include spaces, so space is a safe choice for separating lists). In this case, the browser is going to look for a file named '''hello-web.pde''' located in the same directory as your page page. | ||
How does the browser know how to load a Processing *.pde file? Processing.js takes care of this, and will download, parse (i.e., translate to JavaScript), then run it automatically when the page is loaded. | How does the browser know how to load a Processing *.pde file? Processing.js takes care of this, and will download, parse (i.e., translate to JavaScript), then run it automatically when the page is loaded. | ||
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Processing.js is compatible with Processing, but is not, and will never be, fully compatible with Java. If your sketch uses functions or classes not defined as part of Processing, they are unlikely to work with Processing.js. Similarly, libraries that are written for Processing, which are written in Java instead of Processing, will most likely not work. | Processing.js is compatible with Processing, but is not, and will never be, fully compatible with Java. If your sketch uses functions or classes not defined as part of Processing, they are unlikely to work with Processing.js. Similarly, libraries that are written for Processing, which are written in Java instead of Processing, will most likely not work. | ||
===Processing.js only has two rendering modes=== | |||
Processing has many rendering modes to choose from, depending on the desired quality and speed for graphics (e.g., OPENGL, P3D, JAVA2D, etc.). Processing.js uses <canvas> which provides either a 2D drawing context or a 3D context based on WebGL (a version of OpenGL for the web). Therefore, whatever you choose, you will end-up with either the 2D or 3D context. | |||
===Division which is expected to produce an integer might need explicit casting=== | ===Division which is expected to produce an integer might need explicit casting=== | ||
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</pre> | </pre> | ||
Notice the extra comment line at the top of the code. The '''@pjs''' directive is for Processing.js, and not the developer. Think of it as an extra | Notice the extra comment line at the top of the code. The '''@pjs''' directive is for Processing.js, and not the developer. Think of it as an extra line of code that will be executed before the program begins. | ||
If you have multiple images to load, use a list like so: | If you have multiple images to load, use a list like so: | ||
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===It is possible to put Processing code directly in your web page=== | ===It is possible to put Processing code directly in your web page=== | ||
Using the data-processing-sources attribute on the canvas, and having Processing.js load an external file is the preferred and | Using the data-processing-sources attribute on the canvas, and having Processing.js load an external file is the preferred and recommended way to include scripts in a web page. However, it is also possible to write in-line Processing code. | ||
A few changes are necessary to make the example above work with inline Processing code: | A few changes are necessary to make the example above work with inline Processing code: | ||
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</pre> | </pre> | ||
This code is more complex because it has to figure out which canvas goes with which script (i.e., you can have multiple Processing sketches living in the same page, and therefore, multiple | This code is more complex because it has to figure out which canvas goes with which script (i.e., you can have multiple Processing sketches living in the same page, and therefore, multiple canvases). Also note that the scripts include a '''type''' attribute, which distinguishes between JavaScript and Processing code (the browser will ignore Processing scripts). Finally, note the use of the '''id''' and '''target''' attributes to connect the Processing script with the associated canvas. | ||
Portions of the code above are from the Processing.js project's '''init.js''' file, see http://github.com/annasob/processing-js/blob/0.9.8/examples/init.js. This file will likely be going away in the future, and happen automatically as part of Processing.js initialization. | Portions of the code above are from the Processing.js project's '''init.js''' file, see http://github.com/annasob/processing-js/blob/0.9.8/examples/init.js. This file will likely be going away in the future, and happen automatically as part of Processing.js initialization. | ||