Image compression

Presets vs custom

Picmal ships with six built-in presets that apply sensible quality settings across all image formats. Pick Custom if you want full control over the quality slider for each format.

See compressing files for the presets table.

Lossy formats (Quality 0–100)

These formats use a quality percentage where higher = better quality, larger file.

Format	Range	Default	Notes
JPEG	0–100	85	Most common. 80–90 is usually the sweet spot
WebP	0–100	85	Excellent compression, modern browsers
HEIC	0–100	85	Apple ecosystem, great compression
AVIF	0–100	85	Next-gen, best compression ratios
TIFF	0–100	85	Archival/print use
PDF	0–100	85	Quality of the images inside the PDF — text stays selectable
JP2	0–100	85	JPEG 2000
JXL	0–100	85	JPEG XL
EXR	0–100	85	HDR imagery
PSD	0–100	85	Photoshop files
BMP	0–100	85	Bitmap
TGA	0–100	85	Targa
DDS	0–100	85	DirectDraw Surface
SGI	0–100	85	Silicon Graphics
QOI	0–100	85	Quite OK Image

How PDF compression works

Picmal re-compresses the images embedded inside a PDF and leaves everything else alone: text stays selectable, links keep working, and vector graphics stay sharp.

This matters more than it sounds. A web article saved as PDF often looks like a text document but is almost entirely image data — browsers store photos losslessly when printing to PDF, so a three-page article can carry a single photo that makes up 97% of the file. Picmal re-encodes that photo as JPEG at your chosen quality and typically saves 60–80% without touching a word of the text.

The flip side: a PDF that really is mostly text and fonts has almost nothing to remove. When that happens, Picmal says so — the Saving column shows Already optimized and your original is kept byte-for-byte.

Scanned documents (where each page is one big image) are compressed page-by-page instead, at a resolution derived from the quality slider.

Never larger than the original

When you compress a file, Picmal compares the result against the source and keeps whichever is smaller. If a compression pass wouldn’t actually save space, your original is left untouched — so you never end up with a file bigger than the one you started with.

Compress to a target file size

Need an image under a specific size? Turn on resizing and pick Max File Size, then type a budget like 100 KB or 2 MB. Picmal scales the image down just enough to fit. See resize for details.

Level-based formats (1–9)

These formats use a compression level where higher = more compression, smaller file (but processing takes longer).

Format	Range	Default	Notes
PNG	1–9	9	Lossless — level affects compression effort, not quality
GIF	1–9	7	Higher levels mean more aggressive optimization
SVG	1–9	7	Optimization level for SVG cleanup

PDF rasterization DPI

When converting PDFs to JPG or PNG, Picmal rasterizes each page at a chosen DPI. Higher DPI means sharper output and larger files. Pick the resolution in Settings → Images:

DPI	Best For
72	Quick thumbnails, screen previews
150	General web use (default)
300	Print-ready output
600	High-quality print, fine detail

The default is 150, which keeps output crisp without bloating file sizes on multi-page documents.

Quick Guide: What preset should I use?

Use Case	Recommended Preset
Archiving photos, printing	Maximum quality
Portfolio website, client delivery	High quality
Blog posts, documentation	Balanced
Landing pages, e-commerce	Web optimized
Social media posts	Social media
Email attachments, bandwidth-limited	Maximum compression
Specific needs	Custom