Editing Core Image (section)

== Overview ==
Core Image abstracts the pixel-level manipulation process required when applying a filter to an image, making it simple for applications to implement image transformation capabilities without extensive coding. In a simple implementation, Core Image applies a single ''Image Filter'' to the pixel data of a given source to produce the transformed image. Each Image Filter specifies a single transform or effect, either built into Core Image or loaded from a plugin called an ''Image Unit''. Combined with preset or user-defined input parameters, the filter can be applied to the original pixel data without modifying it, thereby providing non-destructive image editing.<ref name="developer.apple.com">{{cite web | title=Apple - Developer - Developing with Core Image | url=https://developer.apple.com/macosx/coreimage.html | access-date=September 20, 2009 | archive-date=October 6, 2009 | archive-url=https://web.archive.org/web/20091006120044/http://developer.apple.com/macosx/coreimage.html}}</ref><ref>{{cite web | title=Mac Dev Center - Introduction to Core Image Programming Guide - Filter Clients and Filter Creators| url=https://developer.apple.com/mac/library/documentation/GraphicsImaging/Conceptual/CoreImaging/ci_concepts/ci_concepts.html#//apple_ref/doc/uid/TP30001185-CH202-BCIHDIEG | access-date=September 20, 2009}}</ref>

Like [[Photoshop]], Core Image can apply multiple filters to the same image source. Instead of applying a series of filters individually, Core Image assembles a dynamic ''instruction pipeline'' so that only one calculation needs to be applied to the pixel data to achieve a cumulative effect. Applying the pixel operations associated with multiple filters can be achieved simultaneously and without a significant increase in processing time. Regardless of the number of filters, Core Image assembles the code for this instruction pipeline with a [[Just-in-time compilation|just-in-time compiler]], which is executed by either the CPU or graphics card's GPU, whichever can perform the calculation faster.<ref>{{cite web | title=ArsTechnica - Mac OS X 10.4 Tiger - Page 15 | date=April 28, 2005 | url=https://arstechnica.com/reviews/os/macosx-10-4.ars/15 | access-date=September 20, 2009}}</ref>

Filters are written in the ''Core Image Kernel Language'', which shares a subset of commands with [[OpenGL Shading Language| OpenGL Shading Language (GLSL)]].<ref>{{cite web | title=Mac Dev Center - Core Image Kernel Language Reference - Introduction | url=https://developer.apple.com/mac/library/documentation/GraphicsImaging/Reference/CIKernelLangRef/Introduction/Introduction.html | access-date=September 20, 2009}}</ref> When a compatible GPU is available, the Core Image compiler writes the instruction pipeline using GLSL, handling buffers and states transparently. Although GPU rendering is preferred{{Citation needed|reason=False to the best of my knowledge, GPU isn't accurate enough so some calculations always go to the CPU|date=June 2010}}, the compiler can operate in a ''CPU fallback'' mode, generating commands suitable for the current CPU architecture instead.<ref>{{cite web | title=Mac Dev Center - Core Image Programming Guide - Core Image Concepts - Core Image and the GPU | url=https://developer.apple.com/mac/library/documentation/GraphicsImaging/Conceptual/CoreImaging/ci_concepts/ci_concepts.html#//apple_ref/doc/uid/TP30001185-CH202-SW2 | access-date=September 20, 2009}}</ref> CPU fallback uses the [[vector processing]] capabilities of the current CPU or CPUs, and it is multi-processor aware. Thus, Core Image performance depends on the GLSL capabilities of the GPU or the processing power of the CPU. With a supported GPU, most effects can be rendered in realtime or near-realtime.<ref>{{cite web | title=ArsTechnica - Mac OS X 10.4 Tiger - Page 15 | date=April 28, 2005 | url=https://arstechnica.com/reviews/os/macosx-10-4.ars/15 | access-date=April 17, 2007}}</ref>