"File formats: JPEG 2000" configuration dialog

This dialog allows to specify parameters of JPEG 2000 file / stream format.

"Color space" group box

This group box allows you to specify a color space used as an internal format in the JPEG-2000 image.

Click a radio button in this group box to select a required color space.

"Bit depth" group box

This group box allows you to specify a bit depth of each color component.

Table below shows how many colors there are in the images with the different bit detpth:

Bit depth	Colors in the grayscale image	Colors in the color palette image	Colors in the color RGB image
1	2	2	not applied
2	4	4	not applied
4	16	16	not applied
8	256	256	16777216
16	65536	not applied	281474976710656

Click a radio button in this group box to select a required bit depth.

"Compression" group box

Controls in this group box allow you to specify a type of compression used in the JPEG-2000 image.

• Lossless - no color information is lose during compression
• JP2 - lossy JP2 codec
• JPC - lossy JPC codec

"Quality" slide, edit and spin boxes allow you to specify a level of quality for JPEG-2000 compression, from 1 to 1000.

The higher a quality of a compressed the lower level of compression (size of compressed file is bigger). Usually level of quality about 100 - 300 provides very high guality final images (PSNR more than 40).

At the level of quality less than 500, size of the compressed JPEG-2000 file can be estimaged as

            (Size of uncompressed image) * Quality / 1000 .

For example, image with a quality about 200 will be about 5 times smaller than original uncompressed image, and image with the quality about 100 will be about 10 times smaller.

Remarks

If lossless compression is used then color information is not lost in the JPEG-2000 image during compression itself, and a quality of an image converted into the JPEG-2000 format is same as it was the original uncompressed image.

There are two major exceptions from this rule. JPEG-2000 image internally may be presented in the different color spaces and with the different color bit depth. As a result some color information may be lost if during JPEG-2000 compression:

• Color space of the original image is converted into another color space with a smaller number of color components.
• Bit depth of the original image is reduced.

For examlpe, color information is lost when original color image is saved as a gray JPEG-2000 image; or when original image with 8 bit color depth is saved as a 4 bit JPEG-2000 image.