PNG to JPG and Back: 9 Ways to Convert Without Wrecking the Image

PNG and JPG solve different problems, which is why converting between them goes wrong in two specific, predictable ways.

PNG to JPG loses transparency, and the transparent parts usually turn black rather than white. JPG to PNG restores nothing — it takes an already-degraded image and stores it in a container three to eight times larger.

Both conversions are the right answer sometimes. This guide covers nine ways to do them and, more usefully, how to know which direction you actually need.

Which Direction Do You Need?

Your image	Correct format	Why
Photograph	JPG	Smooth gradients compress well, artifacts hide in detail
Screenshot	PNG	Text edges stay sharp, flat colour compresses better
Logo or icon	PNG	Transparency, and hard edges must not blur
Diagram or chart	PNG	Same as above
Scanned document	PNG	JPEG artifacts around letters lower OCR accuracy
Photo with transparency	PNG, or WebP	JPEG cannot store an alpha channel
Photo for a web page	WebP or AVIF	Both beat JPG by 25–50%

Notice that “photograph” is the only row where JPG wins.

The size difference is not a constant — it flips completely depending on the content, which is why a single rule like “PNG is bigger” is wrong. Two measurements on real files:

On a page of text, PNG is 2.6× smaller than JPEG — large flat white areas compress almost perfectly, while JPEG spends bits on artifacts around every letter. On the illustration, the ranking reverses and JPEG is 5.8× smaller.

One caveat worth stating plainly: for a screenshot of a modern web page — anti-aliased text over gradients — JPEG usually still comes out smaller than PNG. It just does so by damaging exactly the edges you care about. The reason to choose PNG there is fidelity, not size.

Pick Your Method First

#	Method	Platform	Batch?	Install?
1	Browser converter	Any	Yes	No
2	macOS Preview and Finder	macOS	Yes	No
3	sips	macOS	Yes	No
4	Windows Paint and Photos	Windows	No	No
5	PowerToys Image Resizer	Windows	Yes	Yes
6	ImageMagick	Any	Yes	Yes
7	Python and Pillow	Any	Yes	Yes
8	GIMP Script-Fu	Any	Yes	Yes
9	Online converters	Any	Yes	No

The Black Background Problem

This is the single most reported issue, and it has a one-line fix.

PNG stores an alpha channel: every pixel carries a transparency value. JPEG has no such channel. When a converter meets a transparent pixel it has to invent a colour, and unless told otherwise many tools use the alpha value itself, which for fully transparent pixels is zero — black.

So a logo with a transparent background becomes a logo on a black rectangle.

# Wrong: transparency becomes black
magick logo.png logo.jpg

# Right: say what the background should be
magick logo.png -background white -alpha remove -alpha off logo.jpg

# On a brand colour
magick logo.png -background "#0F172A" -alpha remove -alpha off logo.jpg

-alpha remove composites the image over the background colour. -alpha off then discards the now-unused channel. Both are needed; using only the first leaves some tools still writing an alpha channel that JPEG cannot hold.

The same applies everywhere. In Photoshop, flatten the image before exporting. In Preview, the export dialog offers no control, so it uses white. In Pillow, you must composite manually — see method 7.

Semi-transparent pixels matter too. A logo with a soft drop shadow has pixels that are 30% opaque. Flattening onto white gives a light grey shadow; flattening onto black gives a dark one. Choose the background that matches where the image will actually sit, or the edges will look wrong.

JPG to PNG Restores Nothing

The other half of the confusion. People convert a JPG to PNG expecting “lossless quality”, and get a much larger file containing exactly the same degraded pixels.

JPEG’s compression is destructive and one-way. It discards high-frequency detail and quantises colour in 8×8 blocks. Once saved, that information does not exist in the file. PNG stores whatever you give it perfectly — including the blocking artifacts, the ringing around edges, and the colour banding.

File	Size	Actual detail
photo.jpg, quality 80	240 KB	Degraded
photo.png converted from it	2.1 MB	Identically degraded

Convert JPG to PNG only for these reasons:

• You are about to edit it and want no further loss during your working passes
• A tool or platform demands PNG — some print services, some upload forms, some game engines
• You need to add transparency by cutting out a background afterwards
• The image is actually a screenshot that someone wrongly saved as JPG, and you want to stop the damage compounding

Otherwise, keep the JPG.

1. A Browser Converter

The quickest route, and the files never leave your machine.

• PNG to JPG
• JPG to PNG
• PNG to WebP — usually the better choice for a web page
• JPG to WebP

Everything runs in the browser through WebAssembly, so you can drop in a batch without an upload wait.

2. macOS Preview and Finder

Finder, for a batch, since macOS Monterey:

1. Select the files
2. Right-click → Quick Actions → Convert Image
3. Choose JPEG or PNG, pick a size, tick Preserve Metadata

Preview, one file: File → Export, choose the format, and for JPEG set the quality slider. Preview flattens transparency onto white with no option to change it.

3. sips

Built into macOS, no install, scriptable.

# PNG to JPG
sips -s format jpeg -s formatOptions 92 image.png --out image.jpg

# JPG to PNG
sips -s format png image.jpg --out image.png

# A whole folder
mkdir -p jpg
for f in *.png; do
  sips -s format jpeg -s formatOptions 92 "$f" --out "jpg/${f%.png}.jpg"
done

sips flattens transparency onto white. If you need a different background colour, use ImageMagick.

4. Windows Paint and Photos

Paint: open the file, File → Save as, choose JPEG picture or PNG picture. Paint flattens transparency onto white and strips all metadata.

Photos: open, ⋯ → Save as, pick the format.

Neither offers a quality setting for JPEG, and neither does batches.

5. PowerToys Image Resizer

The batch answer on Windows without touching a command line.

1. Install Microsoft PowerToys
2. Select any number of images in File Explorer
3. Right-click → Resize with Image Resizer
4. Open Settings in the dialog to set the output format and JPEG quality
5. Choose Actual size if you only want the format change

It writes copies rather than overwriting, and handles hundreds of files.

6. ImageMagick

The most control, and the only method here that lets you choose the flattening colour.

# PNG to JPG, one file
magick photo.png -quality 92 photo.jpg

# A folder
magick mogrify -format jpg -quality 92 *.png

# With explicit flattening, which you almost always want
magick mogrify -format jpg -quality 92 -background white -alpha remove -alpha off *.png

# JPG to PNG
magick mogrify -format png *.jpg

# JPG to PNG with maximum compression effort
magick photo.jpg -define png:compression-level=9 photo.png

# Convert and resize together
magick mogrify -format jpg -quality 88 -resize 2000x2000\> -background white -alpha remove -alpha off *.png

Strip the Metadata, or Keep It Deliberately

# Remove EXIF, GPS and colour profiles
magick mogrify -format jpg -quality 92 -strip *.png

# Keep the colour profile but drop everything else
magick photo.png -quality 92 -strip -profile sRGB.icc photo.jpg

Stripping saves a few kilobytes and removes location data. It also removes the colour profile, which can shift colours on wide-gamut images. Our colour spaces guide explains when that matters.

7. Python and Pillow

# pip install pillow
from PIL import Image

# PNG to JPG, flattening transparency onto white
image = Image.open("logo.png")
if image.mode in ("RGBA", "LA", "P"):
    rgba = image.convert("RGBA")
    background = Image.new("RGB", rgba.size, (255, 255, 255))
    background.paste(rgba, mask=rgba.split()[-1])
    image = background
else:
    image = image.convert("RGB")

image.save("logo.jpg", "JPEG", quality=92, optimize=True, progressive=True)

# JPG to PNG
Image.open("photo.jpg").save("photo.png", optimize=True)

The mask=rgba.split()[-1] argument is what makes semi-transparent pixels blend correctly. Without it, pasting produces hard edges where the soft shadow should be.

progressive=True is worth setting on any JPEG destined for the web. It renders in increasingly sharp passes rather than top to bottom, which looks faster on a slow connection and often produces a slightly smaller file.

8. GIMP Script-Fu

Free, cross-platform, and it handles batches from the command line without you writing a plugin.

gimp -i -b '(let* ((files (cadr (file-glob "*.png" 1))))
  (while (not (null? files))
    (let* ((filename (car files))
           (image (car (gimp-file-load RUN-NONINTERACTIVE filename filename))))
      (gimp-image-flatten image)
      (let ((drawable (car (gimp-image-get-active-drawable image))))
        (file-jpeg-save RUN-NONINTERACTIVE image drawable
                        (string-append filename ".jpg") "" 0.92 0 1 1 "" 0 1 0 0))
      (gimp-image-delete image))
    (setq files (cdr files))))' -b '(gimp-quit 0)'

gimp-image-flatten composites onto the current background colour, which defaults to white. This is worth knowing about mostly because GIMP is already installed on many machines where ImageMagick is not.

9. Online Converters

Fine for images that are already public. Wrong for client artwork, unreleased designs, screenshots of internal tools, or anything under an agreement.

Every local method above avoids the question entirely.

Choosing a JPEG Quality

When you do convert to JPG, the quality number decides everything.

Quality	Use for
95–100	Wasteful in almost all cases
90–92	Archival, or a master you will edit again
80–85	The default for the web
70–75	Large background images that will be scaled
Below 70	Visible blocking on skin and sky

The difference between 85 and 95 is typically 40% more bytes for a difference you cannot see at normal viewing size. Our JPEG optimization guide covers chroma subsampling and the other settings that matter more than the headline number.

Do Not Do This Repeatedly

Every PNG → JPG → PNG → JPG round trip runs the lossy encoder again. Generation loss accumulates: edges get soft, colours drift, blocking spreads.

Keep one master in a lossless format — PNG, TIFF, or the original camera file — and generate the JPGs from it every time. Never edit a JPG and re-save it as a JPG more than once or twice.

Both Are Usually the Wrong Answer for the Web

If the image is going on a web page, neither PNG nor JPG is optimal in 2026.

WebP is 25–35% smaller than JPEG at the same quality, supports transparency, and works in every current browser. AVIF is smaller still, at the cost of slower encoding.

# The conversion that actually helps a web page
magick photo.png -quality 82 photo.webp
magick photo.png -quality 55 photo.avif

Serve those with a JPG or PNG fallback in a <picture> element. See converting images to WebP for the bulk workflow, and the responsive images guide for the markup.

Summary

The Nine Methods

#	Method	Use it when
1	Browser converter	Fast, private, any platform
2	macOS Finder Quick Action	The macOS batch answer
3	sips	Scripted macOS jobs
4	Windows Paint and Photos	One or two files
5	PowerToys Image Resizer	The Windows batch answer
6	ImageMagick	Full control, including flatten colour
7	Python and Pillow	Inside a program
8	GIMP Script-Fu	GIMP is already installed
9	Online converters	Public images only

Checklist

1. ✅ The direction is right — photos to JPG, anything with text to PNG
2. ✅ Transparency was flattened onto a chosen colour, not left to chance
3. ✅ Semi-transparent edges were composited with the alpha as a mask
4. ✅ JPEG quality is 80–85 for the web, 90+ for a master
5. ✅ JPG to PNG was done for a real reason, not to “improve quality”
6. ✅ A lossless master exists, so no round trips are needed
7. ✅ The web version is WebP or AVIF, with PNG or JPG as fallback

For a batch: magick mogrify -format jpg -quality 85 -background white -alpha remove -alpha off *.png. That one line handles the direction most people need and the trap most people hit.