Image File Formats

Independent practical guide. Canonical source: official Image file formats documentation.

Pillow reads and writes the common web and photo formats (JPEG, PNG, WebP, GIF, TIFF, AVIF) plus a long tail of older and specialist ones. Read and write support differ: some formats are read-only (PSD, for example) and PDF is write-only. Run python -m PIL --report to see exactly what your installation supports. For measured file sizes and conversion recipes, see converting between image formats.

* = Requires optional dependency or plugin

JPEG

JPEG is the most common format for photographs. It uses lossy compression that significantly reduces file size but cannot store alpha transparency. The JPEG/JFIF format supports RGB, L, and CMYK modes.

PNG

PNG is a lossless format supporting transparency. It supports modes 1, L, P, RGB, and RGBA. PNG files contain a series of chunks — Pillow exposes most of these via the info dictionary.

PNG DPI metadata

To embed print resolution in a PNG, pass dpi=(x, y) to save(). Pillow writes it to the pHYs chunk; read it back with img.info.get("dpi").

GIF

GIF supports animation and transparency but is limited to 256 colours per frame. Pillow reads and writes GIF files, including animated ones.

WebP (support & save options)

WebP provides both lossy and lossless compression with support for transparency and animation. It generally achieves 25-35% smaller files than JPEG at the same visual quality, making it the recommended format for modern web images.

TIFF

TIFF is a flexible raster format widely used in print, medical imaging, and GIS industries. Pillow supports multi-page TIFF reading, writing, and a variety of compression options.

BMP

BMP is the native Windows bitmap format. It stores uncompressed image data and supports a wide range of pixel depths (1, 4, 8, 16, 24, 32 bit). Modes: 1, L, P, RGB. Writing is limited to these modes.

ICO (Windows Icon)

ICO files contain multiple image sizes in a single file. Pillow can read and write ICO files, embedding multiple sizes.

PDF (Write natively, Read via pdf2image)

Pillow natively exports single-page or multi-page PDF documents. To convert PDF documents into Pillow Images for processing, use the standard pdf2image wrapper around Poppler.

EPS / PS (PostScript)

Pillow can write EPS format and can read it if Ghostscript is installed. Ghostscript must be on the system path for rasterization of EPS to work.

SVG (Read-Only via Plugins)

Pillow's core does not support SVG. To render SVG files with Pillow, use a third-party library such as cairosvg, svglib, or Wand (ImageMagick binding) to first convert the SVG to PNG, then open it in Pillow.

HEIC / HEIF (via plugin)

HEIC is Apple's default photo format since iOS 11. Pillow supports it through the pillow-heif plugin.

Other Supported Formats

Tested: what each format really supports

The tables in this section are printed by Pillow 12.3.0 itself, so they reflect the installed version rather than a list typed by hand.

How many formats Pillow handles

from PIL import Image, features

Image.init()                                                  # load every format plugin
readable, writable = set(Image.OPEN), set(Image.SAVE)
print(len(readable), "formats can be opened,", len(writable), "can be saved")
print("save-only:", sorted(writable - readable))
print("open-only (sample):", sorted(readable - writable)[:12], "...")
print("HEIF/HEIC readable without a plugin:", "HEIF" in readable)
print("codecs:", {name: features.check(name) for name in ["jpg", "zlib", "webp", "avif", "jpg_2000", "libtiff"]})

43 formats can be opened, 30 can be saved
save-only: ['MPO', 'PALM', 'PDF']
open-only (sample): ['CUR', 'DCX', 'FITS', 'FLI', 'FTEX', 'GBR', 'IMT', 'IPTC', 'MCIDAS', 'MPEG', 'PCD', 'PIXAR'] ...
HEIF/HEIC readable without a plugin: False
codecs: {'jpg': True, 'zlib': True, 'webp': True, 'avif': True, 'jpg_2000': True, 'libtiff': True}

Pillow reads far more formats than it writes. PDF is save-only (use pdf2image or PyMuPDF to read PDFs). HEIC/HEIF is missing from both lists: it needs the pillow-heif plugin.

Size, transparency, animation and bit depth per format

import io
from PIL import Image

photo = Image.open("photo.jpg").resize((800, 534))
logo = Image.open("logo.png")                                # RGBA with transparent corners
frames = [photo, photo.transpose(Image.Transpose.FLIP_LEFT_RIGHT)]


def save(img, fmt, **kw):
    buf = io.BytesIO()
    img.save(buf, fmt, **kw)
    buf.seek(0)
    return buf


def check(fn):
    try:
        return fn()
    except Exception:
        return "-"


print(f"{'format':<9}{'photo KB':>9}  {'keeps alpha':<12}{'animation':<10}{'16-bit grey'}")
grey16 = photo.convert("I").point(lambda v: v * 257).convert("I;16")
for fmt in ["JPEG", "PNG", "WEBP", "AVIF", "GIF", "TIFF", "BMP", "JPEG2000", "TGA", "PPM"]:
    kb = check(lambda: f"{save(photo, fmt).getbuffer().nbytes / 1024:.0f}")
    alpha = check(lambda: "yes" if Image.open(save(logo, fmt)).convert("RGBA").getpixel((2, 2))[3] == 0 else "no")
    anim = check(lambda: "yes" if getattr(Image.open(save(frames[0], fmt, save_all=True, append_images=frames[1:])),
                                         "n_frames", 1) > 1 else "no")
    deep = check(lambda: "yes" if Image.open(save(grey16, fmt)).mode in ("I;16", "I", "I;16B") else "no")
    print(f"{fmt:<9}{kb:>9}  {alpha:<12}{anim:<10}{deep}")

format    photo KB  keeps alpha animation 16-bit grey
JPEG            39  -           -         -
PNG            426  yes         yes       yes
WEBP            28  yes         yes       no
AVIF            34  yes         yes       no
GIF            152  yes         yes       no
TIFF          1252  yes         yes       yes
BMP           1252  no          -         -
JPEG2000       411  yes         -         yes
TGA           1252  yes         -         -
PPM           1252  no          -         yes

"-" means saving raised an error; "no" means the file saved, but the feature was lost when it was opened again. The photo sizes use each format's default settings, so they compare defaults rather than best-case compression; see reducing file size and converting formats for tuned settings. GIF keeps transparency as a single palette entry, so soft edges become hard, and it has at most 256 colours per frame. PNG's "yes" for animation is APNG, which browsers play but many image viewers show as a still. BMP writes 32-bit pixels including the alpha byte, but with a header that does not declare an alpha channel, so readers (Pillow included) open it as plain RGB: hence "no".