Better Portable Graphics
| Filename extension | .bpg |
|---|---|
| Magic number | 42 50 47 fb |
| Initial release | 2014 |
| Type of format | lossy lossless bitmap image format |
| Extended from | HEVC |
| Open format? | Yes |
| Website | bellard |
Better Portable Graphics (BPG) is a file format for coding digital images, which was created by programmer Fabrice Bellard in 2014. Its purpose is to be a more compression-efficient replacement for the JPEG image format when quality or file size is an issue.[1] It is based on the intra-frame encoding of the High Efficiency Video Coding (HEVC) video compression standard.[2] Tests have shown that BPG produces significantly smaller files for a given quality than any other graphics file format.[3]
Contents
High Efficiency Video Coding and BPG[edit]
HEVC already has several profiles defined for still-picture coding using HEVC's intra-frame encoding for various bit depths and color formats, including the progressively more capable Main Still Picture, Main 4:4:4 Still Picture, and Main 4:4:4 16 Still Picture profiles.
BPG is essentially a wrapper for uses of the HEVC's Main 4:4:4 16 Still Picture profile up to 14 bits per sample.
Specifications[edit]
BPG's container format is intended to be more suited to a generic image format than the raw bitstream format used in HEVC (which is otherwise ordinarily used within some other wrapper format, such as the .mp4 file format).[2][4]
BPG supports the color formats known as 4:4:4, 4:2:2, and 4:2:0.[2] Support for a separately coded extra channel is also included for an alpha channel or the fourth channel of a CMYK image.[2] Metadata support is included for Exif, ICC profiles, and XMP.[2]
Color space support is included for YCbCr with ITU-R BT.601, BT.709, and BT.2020 (non-constant luminance) definitions, YCgCo, RGB, CMYK, and grayscale.
Support for HEVC's lossy and lossless data compression is included.
Patents[edit]
BPG is believed to be covered by some of the patents on HEVC, which makes LWN.net conclude that it is unlikely that BPG will replace JPEG, despite BPG's technical superiority.[4] There doesn't seem to be any evaluation available online of which patents affect BPG. This also means that it is not yet known when any patents will expire, and BPG would therefore become patent-free. Given the 20-year term of US patents and the 2013 publishing date of HEVC (first draft published in 2010), the expiry date of latest covering patent should be no later than 2033.
Other proposed JPEG replacements[edit]
Several previous image formats are also technically superior to JPEG for similar uses, though not by the same margin as BPG. They have found some niche uses, but have crucially not gained acceptance on the web. Investigations for a possible JPEG replacement have included:[3][5]
References[edit]
- ^ "BPG Image format". Fabrice Bellard. 2014. Retrieved 2014-06-12.
- ^ a b c d e "BPG specification". Retrieved December 2014.
- ^ a b "Lossy Compressed Image Formats Study". Mozilla Corporation. Retrieved 2015-02-10.
- ^ a b "BPG, a still-image format from video compression". LWN.net.
- ^ "BPG Image Comparison". Retrieved 2015-02-10.
External links[edit]
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