cbconvert

reads CBR (RAR), CBZ (ZIP), CB7 (7Z), CBT (TAR), PDF, EPUB, MOBI, CHM, DOCX, PPTX and plain directory
saves processed files in ZIP archive format or TAR
images can be converted to JPEG, PNG, TIFF, WEBP, AVIF, JXL, or 4-Bit BMP (16 colors) image format
rotate, adjust brightness/contrast or grayscale images
resize filters (NearestNeighbor, Box, Linear, MitchellNetravali, CatmullRom, Gaussian, Lanczos)
export covers from comics
create thumbnails from covers by FreeDesktop specification

Download

Download the latest binaries from the releases.

Linux Flatpak is available at Flathub.

Compile

Install to GOBIN (you can point GOBIN to e.g. /usr/local/bin or ~/.local/bin):

go install github.com/gen2brain/cbconvert/cmd/cbconvert@latest

For GUI app, check IUP requirements, and then install:

go install github.com/gen2brain/cbconvert/cmd/cbconvert-gui@latest

Using cbconvert in file managers to generate FreeDesktop thumbnails

Copy/install cbconvert cli binary to your PATH, create file ~/.local/share/thumbnailers/cbconvert.thumbnailer and paste contents from thumbnailer.

This is what it looks like in the PCManFM file manager:

Using command line app

Usage: cbconvert <command> [<flags>] [file1 dir1 ... fileOrDirN]


Commands:

  convert
    	Convert archive or document

    --profile
    	Load a saved GUI profile as defaults; explicit flags still override (default "")
    --width
    	Image width (default "0")
    --height
    	Image height (default "0")
    --fit
    	Best fit for required width and height (default "false")
    --no-upscale
    	Do not upscale images already smaller than the requested width/height (default "false")
    --dpi
    	Document rendering resolution in DPI (PDF, EPUB, etc.), 0 uses the default (300) (default "0")
    --format
    	Image format, valid values are jpeg, png, tiff, bmp, webp, avif, jxl (default "jpeg")
    --archive
    	Archive format, valid values are zip, tar (default "zip")
    --zip-level
    	ZIP compression level, 0 disables compression, 1-9 sets deflate level (1 fastest, 9 smallest), -1 uses the default (default "-1")
    --quality
    	Image quality (default "75")
    --effort
    	Encoder speed/effort, format-specific (webp method 0-6, avif speed 0-10, jxl effort 1-7), -1 uses the format default (default "-1")
    --lossless
    	Lossless compression (webp, avif, jxl), ignores quality (default "false")
    --combine
    	Combine all inputs into a single archive (default "false")
    --outfile
    	Output file name for --combine (default: first input + -combined) (default "")
    --filter
    	0=NearestNeighbor, 1=Box, 2=Linear, 3=MitchellNetravali, 4=CatmullRom, 5=Gaussian, 6=Lanczos (default "2")
    --no-cover
    	Do not convert the cover image (default "false")
    --no-rgb
    	Do not convert images that have RGB colorspace (default "false")
    --no-nonimage
    	Remove non-image files from the archive (default "false")
    --no-convert
    	Do not transform or convert images (default "false")
    --grayscale
    	Convert images to grayscale (monochromatic) (default "false")
    --rotate
    	Rotate images, valid values are 0, 90, 180, 270 (default "0")
    --brightness
    	Adjust the brightness of the images, must be in the range (-100, 100) (default "0")
    --contrast
    	Adjust the contrast of the images, must be in the range (-100, 100) (default "0")
    --suffix
    	Add suffix to file basename (default "")
    --outdir
    	Output directory (default ".")
    --size
    	Process only files larger than size (in MB) (default "0")
    --recursive
    	Process subdirectories recursively (default "false")
    --quiet
    	Hide console output (default "false")

  cover
    	Extract cover

    --profile
    	Load a saved GUI profile as defaults; explicit flags still override (default "")
    --width
    	Image width (default "0")
    --height
    	Image height (default "0")
    --fit
    	Best fit for required width and height (default "false")
    --no-upscale
    	Do not upscale images already smaller than the requested width/height (default "false")
    --dpi
    	Document rendering resolution in DPI (PDF, EPUB, etc.), 0 uses the default (300) (default "0")
    --format
    	Image format, valid values are jpeg, png, tiff, bmp, webp, avif (default "jpeg")
    --quality
    	Image quality (default "75")
    --effort
    	Encoder speed/effort, format-specific (webp method 0-6, avif speed 0-10, jxl effort 1-7), -1 uses the format default (default "-1")
    --lossless
    	Lossless compression (webp, avif, jxl), ignores quality (default "false")
    --filter
    	0=NearestNeighbor, 1=Box, 2=Linear, 3=MitchellNetravali, 4=CatmullRom, 5=Gaussian, 6=Lanczos (default "2")
    --outdir
    	Output directory (default ".")
    --size
    	Process only files larger than size (in MB) (default "0")
    --recursive
    	Process subdirectories recursively (default "false")
    --quiet
    	Hide console output (default "false")

  thumbnail
    	Extract cover thumbnail (freedesktop spec.)

    --profile
    	Load a saved GUI profile as defaults; explicit flags still override (default "")
    --width
    	Image width (default "0")
    --height
    	Image height (default "0")
    --fit
    	Best fit for required width and height (default "false")
    --no-upscale
    	Do not upscale images already smaller than the requested width/height (default "false")
    --dpi
    	Document rendering resolution in DPI (PDF, EPUB, etc.), 0 uses the default (300) (default "0")
    --filter
    	0=NearestNeighbor, 1=Box, 2=Linear, 3=MitchellNetravali, 4=CatmullRom, 5=Gaussian, 6=Lanczos (default "2")
    --outdir
    	Output directory (default ".")
    --outfile
    	Output file (default "")
    --size
    	Process only files larger than size (in MB) (default "0")
    --recursive
    	Process subdirectories recursively (default "false")
    --quiet
    	Hide console output (default "false")

  meta
    	CBZ metadata

    --cover
    	Print cover name (default "false")
    --comment
    	Print zip comment (default "false")
    --comment-body
    	Set zip comment (default "")
    --file-add
    	Add file to archive (default "")
    --file-remove
    	Remove file from archive (glob pattern, i.e. *.xml) (default "")

  version
    	Print version

Examples

Rescale images to 1200px for all supported files found in a directory with a size larger than 60MB:

cbconvert --recursive --width 1200 --size 60 /media/comics/Thorgal/

Convert all images in pdf to 4bit BMP images and save the result in ~/comics directory:

cbconvert --format bmp --outdir ~/comics /media/comics/Garfield/Garfield_01.pdf

BMP format is a very good choice for black&white pages. Archive size can be smaller 2-3x and the file will be readable by comic readers.

Extract covers to ~/covers dir for all supported files found in the directory, Lanczos algorithm is used for resizing:

cbconvert cover --outdir ~/covers --filter=7 /media/comics/GrooTheWanderer/

Convert all images to AVIF format:

cbconvert --format avif --quality 50 --width 1280 --outdir ~/comics /media/comics/Misc/

Combine several issues into a single archive:

cbconvert convert --combine --outfile Series.cbz --outdir ~/comics issue1.cbz issue2.cbr issue3.cb7

Quality settings

This table maps quality settings for JPEG to the respective AVIF and WEBP quality settings:


JPEG quality	50	60	70	80
AVIF quality	48	51	56	64
WEBP quality	55	64	72	82