Instead of creating a separate program to direct the operation of the GPU, there was a set of fixed functions that you used to render objects on the screen. OpenGL ES 1.1 did not use shaders - it used what is called a fixed-function pipeline. If you've been doing iOS programming since at least iOS 5, you might be aware that there was a shift in OpenGL programming on the iPhone, from OpenGL ES 1.1 to OpenGL ES 2.0. We're going to take a short trip in The Wayback Machine to get an overview of what a shader is and how it came to be an integral part of our workflow. The purpose of this article is to get your feet wet with some foundation information necessary to get you going on your journey to writing your own image processing shaders. This process can be incredibly daunting, especially to newer developers. The concepts we are going over here even map well to custom kernels in Core Image, although they use a slightly different syntax. You can take the concepts from GLSL and apply them to other, more proprietary languages like the Metal Shading Language. There are many shading languages out there on the market, but the one you should focus on if you are doing OS X or iOS development is the OpenGL Shading Language, or GLSL. A shader is a small, C-based program written in a shading language. The tool we use to take advantage of this power is a shader. Being able to filter high-quality live video on your phone is impractical or even impossible without GPU-based processing. The CPU is a generalist that has to deal with everything, while your GPU can focus on doing one thing really well, which is doing floating-point math in parallel it turns out that image processing and rendering is nothing more than doing a lot of floating-point math on the values for the pixels that render to your screen.īy effectively utilizing your GPU, you can increase graphics-rendering performance on your phone by a hundred fold, if not a thousand fold. Your phone contains two different processing units, the CPU and the GPU. There are many ways to process images on your computer or mobile phone, but by far the most efficient is effectively using your Graphics Processing Unit, or GPU. In spite of how divergent these applications are, both of these examples go through the same process from creation to rendering. Image processing can be as simple as converting a photo to grayscale and as complex as analyzing a video of a crowd for a specific person. All of these applications are used to do image processing.
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