Documentation - PicDock

Image Format Conversion & Compression

PicDock provides powerful batch export and compression tools built directly into the app. This guide explains how different image formats are handled during export and compression operations.

Supported Input Formats

PicDock can read and display the following image formats:

JPG/JPEG – Standard lossy compression format
PNG – Lossless format with transparency support
HEIC/HEIF – Apple's high-efficiency format
TIFF – High-quality format often used in professional workflows
WebP – Modern web format from Google
GIF – Animated and static graphics
BMP – Windows bitmap format
SVG – Scalable vector graphics

Supported Output Formats

When exporting, PicDock can encode images to:

JPEG – Best for photos and complex images
PNG – Best for graphics with transparency or sharp edges
HEIC – Best for Apple ecosystem with excellent compression

Export Conversion Matrix

The table below shows how each input format can be converted during export:

Input Format	→ JPEG	→ PNG	→ HEIC	Keep Original
JPG/JPEG	✅	✅	✅	✅ JPEG
PNG	✅	✅	✅	✅ PNG
HEIC/HEIF	✅	✅	✅	⚠️ JPEG*
TIFF	✅	✅	✅	⚠️ JPEG
WebP	✅	✅	✅	⚠️ JPEG
GIF	✅	✅	✅	⚠️ JPEG
BMP	✅	✅	✅	⚠️ JPEG
SVG	✅	✅	✅	⚠️ JPEG

Legend:

✅ = Fully supported conversion
⚠️ = Falls back to JPEG (original format not supported for output encoding)

Compression Format Handling

When using PicDock's Smart Compression feature, formats are handled as follows:

Format	Compression Behavior
JPEG	✅ Compressed as JPEG with quality setting
PNG	✅ Optimized with pngquant OR converted to JPEG (user choice)
HEIC/HEIF	✅ Compressed as HEIC with quality setting
GIF	⏭️ Skipped – "GIF files are not supported for compression"
SVG	⏭️ Skipped – "SVG is a vector format and cannot be compressed"
WebP, TIFF, BMP	🔄 Converted to JPEG silently

Quality Settings

JPEG and HEIC: Support quality adjustment from 10% to 100%
PNG: Always lossless (quality setting not applicable)

Important Limitations

1. WebP Output Not Supported

macOS's native CGImageDestination API cannot encode WebP format. When you select "Keep Original" for a WebP image, it will be converted to JPEG instead.

2. HEIC "Keep Original" Behavior

For maximum compatibility, HEIC images fall back to JPEG with a .jpg extension when "Keep Original" is selected. This is intentional to ensure the exported files work everywhere.

3. Animated GIF Limitation

Animated GIFs will lose their animation during export. The result will be a single-frame image in your chosen output format (JPEG, PNG, or HEIC).

4. SVG Rasterization

SVG files are vector-based and will be rasterized (converted to pixels) during export. The output resolution depends on your export size settings. For best results with SVG, choose a specific output resolution rather than relying on the original dimensions.

Best Practices

For web optimization: Export as JPEG with 80-85% quality for photos, or PNG for graphics with transparency.
For Apple ecosystem: HEIC offers excellent quality at smaller file sizes, perfect for sharing between Apple devices.
For archival: Keep originals in their native format when possible. Use PNG for lossless preservation.
For batch compression: Select multiple images and let PicDock handle format-specific optimization automatically.