色調補正
明るさ、コントラスト、彩度などを細かく微調整します。
About Adjust Colors
Fine-Tune Your PDF’s Appearance
Adjust Colors gives you four controls: brightness (-100 to +100), contrast (-100 to +100), gamma correction (0.1 to 5.0), and a sepia tone toggle. Move the sliders, see the result in real time on your actual pages, then apply when it looks right.
The tool renders each page to canvas, applies the adjustments pixel by pixel, and rebuilds the PDF at 2x resolution. Everything happens in your browser — your file never leaves your device.
When to Adjust PDF Colors
Color adjustments fix problems and improve readability. Different situations call for different settings.
Fix Scanned Documents
Scanned pages often come out too dark, too light, or washed out. Adjust brightness and contrast to make text sharp and readable.
Print Preparation
Colors on screen don’t always match print. Tweak brightness and contrast so printed output matches what you expect.
Photo-Heavy PDFs
PDFs with photographs benefit from gamma correction and contrast adjustments. Fine-tune images without opening a separate editor.
Sepia Effect
Apply a warm sepia tone for a vintage or aged-paper look. Works well on documents meant for display or design projects.
What Each Slider Does
Brightness shifts all pixels lighter or darker. Contrast increases or decreases the difference between light and dark areas. Gamma correction adjusts midtone brightness without blowing out highlights or crushing shadows — useful for scanned documents where the overall lightness is off but the extremes are fine.
Sepia applies a warm brownish tone across the entire document. All four adjustments stack: you can boost contrast, darken slightly, and apply sepia in one pass. A reset button returns everything to defaults.
How It Compares
PDF color adjustment tools are uncommon. Most require image editing software and a round-trip through export/reimport.
| 機能 | OxygenPDF | Adobe Acrobat | iLovePDF |
|---|---|---|---|
| Brightness adjustment | Preflight | ||
| Contrast adjustment | Preflight | ||
| Gamma correction | Preflight | ||
| Sepia tone | |||
| Live preview | |||
| Batch processing | |||
| No file upload required | Desktop only | ||
| Free to use |
Nothing Leaves Your Machine
Color adjustments run entirely in your browser. Pages are rendered, processed, and rebuilt locally. The adjusted PDF downloads straight to your machine.
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