⚠️🚧 In development and very experimental 🚧⚠️

To do

• write the todo list
• get actions to use gcc-12+
• look at task lists
• switch to cmake / something modern?
• Consider plain C interface
• Write public API first
• Investigate variable quantization by edge/centre distance or mask

jpeglevel

• Adjust jpeg luminosity and/or chroma levels without re-compressing and losing quality.
• Operates within YCbCr colour space by directly adjusting the JPEG DCT blocks.
• Does not need to make lossy requantisation or YCbCr ➤ RGB ➤ YCbCr conversion.
• Allows adjustments to brightness/contrast without affecting colour
• Allows adjustments to colour intensity
• Allows shifting Cb, Cr to ajust colour balance
• Analyses all YCbCr values to produce histograms and stats
• Calculates ranges of Y, Cb, Cr changes that remain within RGB colourspace
• Or allows changes that just push a specified number/percentage of pixels outside RGB colourspace

Requirements

• Uses the libjpeg-turbo library C++ API TurboJPEG
• Written in C++ for GCC with -std=gnu++20
• Uses standard autotools