You’ve probably saved 1000s of JPEG images, but do you know what exactly JPEG does? Our smartphones and cameras save images in JPEG format, furthermore, the majority of images you see on the internet are saved using JPEG compression.
source/image(PrtSc): Branch Education
This format is everywhere, but do you know exactly how it works? Well in this video we’re going to explore the JPEG compression format. This is a rather complicated video, so it may take watching it a few times through to understand it all.
JPEG uses a lossy form of compression based on the discrete cosine transform (DCT). This mathematical operation converts each frame/field of the video source from the spatial (2D) domain into the frequency domain (a.k.a. transform domain). A perceptual model based loosely on the human psychovisual system discards high-frequency information, i.e. sharp transitions in intensity, and color hue.
In the transform domain, the process of reducing information is called quantization.The compression method is usually lossy, meaning that some original image information is lost and cannot be restored, possibly affecting image quality. There is an optional lossless mode defined in the JPEG standard. However, this mode is not widely supported in products./wikipedia