How to convert JPG to PNG on iPhone
Let's deal with the myth first: converting a JPG to a PNG does not improve the image. It cannot. The damage was done when the JPG was written, and no later format can invent the detail back. What PNG gives you is a guarantee that no further loss happens.
PNG is not an upgrade path. A JPG has already discarded high-frequency detail and quantised what remained. Encoding those pixels losslessly preserves them perfectly — including every compression artefact. You end up with a file that is typically 5–10x larger and looks identical. If a tool or a person promises PNG conversion will “enhance” or “restore” a JPG, they are selling something.
What the two formats really do
JPG (JPEG, 1992) is a lossy photographic codec. It works in the frequency domain: the image is split into 8x8 blocks, transformed with a DCT, and the coefficients your eye cares least about are quantised away. That is why it is small, and why heavy compression produces blocky 8x8 squares and ringing around sharp edges.
PNG (1996) is lossless. DEFLATE compression, an optional 8-bit alpha channel, no generation loss ever. Built for graphics, not photographs — which is why photographic PNGs are so large.
Good reasons to actually do this
- You are about to edit and re-save repeatedly. This is the strongest reason. Each JPG save re-quantises the image and compounds artefacts — crop, save, adjust, save, and the degradation accumulates visibly. Convert to PNG once, do all your edits in PNG, then export to a lossy format at the end if you need to.
- You need to add transparency. JPG cannot store an alpha channel. If you are cutting out a background or building a logo overlay, you need a format that can hold the alpha — PNG is the one everything understands.
- A pipeline demands PNG. App icons, some design tools, certain print and CMS workflows accept nothing else.
- Archival of a graphic. If someone handed you a JPG of a chart or a scanned document, PNG at least stops it getting worse each time it is touched.
Bad reasons
- “To make it higher quality.” It won't. See above.
- “To make it print better.” It won't. Print quality depends on the pixel dimensions and DPI you print at, not the container.
- “To remove JPG artefacts.” PNG will lovingly preserve every single one of them, in a bigger file.
No quality slider appears for PNG. Convexy only shows one for lossy formats — JPG, HEIC, WebP and AVIF — because only they have a quality/size dial. PNG is lossless: the only way to make it smaller is to reduce the pixel dimensions, which you can do with the resize option in Options.
The size jump is not a bug
A 500 KB JPG photo will commonly become a 4–6 MB PNG. Lossless compression cannot compress the noise-like, high-entropy data that a photograph is mostly made of. If the file size is a problem and you do not need transparency or a lossless working copy, keep the JPG — or use WebP, which gets you a modern codec and a much smaller file.
The conversion itself runs entirely on your iPhone or iPad through Apple's ImageIO frameworks. No upload, no account, no server — it works with the network off.
How to do it
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Pick the JPG
Tap Browse files, choose from Photos, or share the image into Convexy from any app.
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Choose PNG
Convexy lists only the formats this file can actually become. Tap PNG.
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Resize if you need to (optional)
PNG has no quality slider because it is lossless. If the resulting file is too big, set a maximum dimension in Options — the image is scaled down proportionally with high-quality interpolation.
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Convert
The result screen shows the original and output sizes side by side, so the size increase is never a surprise.
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Save or share
Rename the output if you want, then save it to Files or Photos, or send it on through the share sheet.
Common questions
Does converting JPG to PNG improve image quality?
No. This is the single most common misconception about image formats. The JPG permanently discarded data when it was created. PNG is lossless, so it preserves the pixels it is given exactly — artefacts included. The result looks identical and is much larger. The only quality benefit is forward-looking: further edits and saves won't degrade it any more.
Can I remove JPG compression artefacts by converting to PNG?
No. The artefacts are baked into the pixel values — they are the image now, as far as any format is concerned. Removing them requires an actual restoration or denoising algorithm that guesses at the original, not a format change. A format conversion moves pixels between containers; it does not repair them.
Will converting to PNG add transparency to my JPG?
Not by itself. The PNG will have the capability to store an alpha channel, but every pixel from the JPG is fully opaque. You still have to remove the background yourself in an editor. Converting to PNG is the necessary first step — it just isn't the whole job.
Why is the PNG so much larger than the JPG?
Because JPG threw away most of the data and PNG throws away none. Photographic detail and sensor noise are close to random, and lossless compression cannot shrink randomness. A 5x to 10x size increase converting a photo from JPG to PNG is completely normal.
Should I use PNG or WebP for a JPG I want to keep editing?
PNG, if the priority is a working file that every tool on earth can open without argument. WebP is the better pick if you also care about size — it supports transparency, and in Convexy pushing the quality slider to 100% switches libwebp into its lossless mode, so you can get a lossless WebP that is still smaller than the equivalent PNG. The catch is tool support: PNG is accepted everywhere, WebP is not.