bookc — Image Folder → Publishing-Ready PDF

bookc converts a folder of images into a professional, publishing-ready PDF. Each image gets its own page, scaled to fill edge-to-edge with no whitespace and no cropping — perfect for digital photo books, portfolios, and illustrated documents.

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Features

• One image per page — clean, full-bleed layout
• Smart scaling — images fill the page completely regardless of their original pixel size; aspect ratio is always preserved and images are never upscaled beyond their native resolution
• 16:9 landscape pages — page dimensions are derived from your images (297 × 167 mm), not from a standard paper size, so there is zero whitespace on any edge
• Alphabetical ordering — files are sorted by filename, so sequential naming schemes (e.g. 001_intro.jpg, 002_chapter.png) are handled automatically
• Mixed formats — JPG and PNG images can coexist in the same folder
• Fast — image headers are read without fully decoding pixel data, so large folders process quickly
• No dependencies at runtime — compiles to a single self-contained binary

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Requirements

Tool	Version	Install
Go	1.21+	https://go.dev/dl/

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Installation

1. Clone or download the source

git clone https://github.com/yourname/bookc.git
cd bookc

Or simply place main.go, go.mod, and go.sum in a folder named bookc.

2. Download dependencies

go mod tidy

This fetches the only external dependency: github.com/jung-kurt/gofpdf.

3. Build the binary

go build -o bookc .

This produces a single executable named bookc (or bookc.exe on Windows) in the current directory. No installer needed — move it anywhere you like.

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Usage

./bookc <image-folder> <output.pdf>

Argument	Description
<image-folder>	Path to the folder containing your image files
<output.pdf>	Path and filename for the generated PDF

Example

chaschel@linux:~/Documents/go/bookc$ ./bookc ./images output.pdf
Found 4 image(s). Generating PDF…
  [1/4] noli_1-a.png
  [2/4] noli_1-b.png
  [3/4] noli_7-a.png
  [4/4] noli_7-f.jpg

Done → output.pdf

The PDF is written to output.pdf in the current working directory. You can specify any path for the output, e.g.:

./bookc ./photos ~/Desktop/my-book.pdf
./bookc /home/user/scans /mnt/nas/archive/book.pdf

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Image Requirements

Property	Details
Formats	.jpg, .jpeg, .png
Orientation	Landscape recommended; portrait images are scaled to fit
Naming	Any scheme — files are sorted alphabetically by filename
Size	Any resolution; tested with images up to 2816 × 1536 px

Tip: Name your files so they sort in the order you want them to appear, for example: 001_cover.jpg, 002_chapter1.png, 003_chapter2.jpg. Leading zeros ensure correct alphabetical ordering beyond 9 files.

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Output Specification

Property	Value
Page size	297 × 167 mm (16:9 landscape, custom)
Orientation	Landscape
Margins	None — full bleed
Images per page	1
Image scaling	Fit to fill, aspect ratio preserved
Upscaling	Never — images are only scaled down
PDF version	1.3 (compatible with all viewers)
Metadata	Creator and Producer fields embedded

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Customisation

All layout constants are defined at the top of main.go. Edit them and rebuild to change the output.

const (
    pageW = 297.0               // mm — page width
    pageH = 297.0 * 9.0 / 16.0 // mm — page height, derived from 16:9 ratio
)

Change to a different aspect ratio

For a 4:3 image set:

pageH = 297.0 * 3.0 / 4.0  // ≈ 222.75 mm

Add a uniform margin

const margin = 10.0  // mm

// In the build loop, replace the fitInBox call with:
fitW, fitH := fitInBox(float64(pixW), float64(pixH), pageW-2*margin, pageH-2*margin)
x := margin + (pageW-2*margin-fitW)/2
y := margin + (pageH-2*margin-fitH)/2

Rebuild after any change:

go build -o bookc .

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Troubleshooting

no supported images found in: ./images

• Check that the folder path is correct and contains .jpg, .jpeg, or .png files.
• Hidden files (starting with .) and sub-folders are ignored automatically.

cannot read image: decode config

• The image file may be corrupted or in an unsupported format (e.g. WebP, TIFF).
• Convert it to JPG or PNG first using any image editor or ffmpeg:

  ffmpeg -i input.webp output.jpg

PDF opens in portrait orientation

• Ensure you are running the binary built from the latest main.go.
• Some PDF viewers default to portrait — check your viewer's View or Page Display settings and set it to Landscape or Auto-rotate.

Images appear in the wrong order

• bookc sorts files alphabetically by filename. Rename files so they sort in your intended sequence using zero-padded numbers: 001_, 002_, 003_ … rather than 1_, 2_, 10_.

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Project Structure

bookc/
├── main.go      — full source code (~175 lines)
├── go.mod       — module definition and Go version
├── go.sum       — dependency checksum lock file
└── README.md    — this file

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Dependencies

Package	Purpose
github.com/jung-kurt/gofpdf v1.16.2	PDF generation

Standard library packages used: fmt, image, image/jpeg, image/png, log, os, path/filepath, sort, strings.

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License

MIT — do whatever you like with it.