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Joint Photographic Expert Group Definition

Joint Photographic Expert Group is the group that has created the JPEG graphic format with lossy compression that achieves high compression rates.

The JPEG group created a graphic file format that is used to display high-resolution color images. JPG and JPEG images apply a user-specified compression scheme that can significantly reduce the large file sizes typically associated with photo-realistic color images.

The JPEG group follows the ISO / ITU-TSS standard to compress images using discrete cosine transformation.

It provides lossy compression (original sharpness is lost) and can deliver ratios of 100: 1 and higher.

JPEG is completely image dependent, but 10: 1 and 20: 1 ratios can provide less noticeable loss.

The more the loss can be tolerated, the more the image can be compressed.

Compression can be achieved by dividing the frame into small blocks of pixels, which are halved over and over again until the ratio is achieved.

The characteristics of the JPEG graphic format are:

  • Bitmap graphic format.
  • True color support, also known by its English namesake true color (24 Bit).
  • Compression algorithm (lossy) that supports high pack rates (1/20 and more).
  • The support of true color (24 bits) of JPEG offers us the possibility of offering images with a depth of 16,777,216 colors.

It is clear that a bitmap with this color depth reaches huge memory sizes, but this is supplemented by the compression algorithm that the format offers.

This compression algorithm, although very powerful (reduces the size of the bitmap to 5% of the original or less), offers information losses as we increase its compression rate. The compression rate is adjusted when we save the file, for example, from our image processor.

This loss of information occurs as we increase its compression rate and is noticeable in the resolution of the image.