Make a low-resolution image higher resolution

Resolution is pixels, not DPI

An image's resolution is its size in pixels, written as width by height. A 400 x 300 photo holds 120,000 pixels, while a 1024 x 1024 image holds just over a million, or about one megapixel. Every edge, texture and letter has to fit into those pixels, so a small image has little room for fine detail.

DPI (more precisely PPI, pixels per inch) is something else: a number stored in the file that tells printing software how many pixels to fit into each inch of paper. Changing it from 72 to 300 without resampling leaves every pixel as it was. The image would print smaller, but it looks identical on screen and gains no detail.

Small images usually have ordinary origins: thumbnails and avatars, graphics saved for the web when screens were smaller, photos from early camera phones that recorded 640 x 480 pixels, crops from bigger photos, or copies shrunk by a site that resizes uploads. Once those pixels are gone from the file, no setting brings them back.

Why a resized image looks soft

When you enlarge an image in an editor or a browser, most pixels in the bigger version are new, and the software has to calculate a value for each one. Taking a 250 x 250 avatar to 1000 x 1000 multiplies the pixel count by 16, so 15 of every 16 pixels in the result were never in your file.

The simplest method, nearest neighbor, copies the closest original pixel into each gap and leaves hard blocks. Bilinear and bicubic interpolation, the usual defaults, blend nearby pixels into smooth in-between values instead. That hides the blocks, but an edge that went from dark to light across two pixels becomes a gentle ramp many pixels wide, and fine texture flattens into smooth patches.

Nothing is lost, but nothing is gained either: the same information is spread over more pixels, so the image looks blurrier the larger you show it. A sharpening filter can make edges look a little crisper, but it cannot put back texture the file never held.

How AI upscaling adds new detail

An AI upscaler fills the new pixels with predictions instead of averages. Its model has learned from vast numbers of images how things like eyelashes, brickwork, lettering and leaves usually look at high resolution, and it draws your small image larger with that kind of detail in place.

Pixelperfect uses Google's image AI for this. Each image is sent with a written request to upscale it, sharpen fine detail, remove noise and JPEG compression artifacts, and reconstruct crisp edges. The same request tells it to preserve the exact subject, composition, framing and colors, and to add, remove or restyle nothing.

What it adds is a prediction, not a recovery: the model draws what probably belongs in the missing pixels, not what was actually there. In text just 6 or 7 pixels tall, an "e" and a "c" can look almost identical, and the model may draw a crisp "c" where the original said "e". Sharp does not mean correct.

Image models improve partly because people are paid to compare their outputs side by side and judge whether the added detail is faithful, and AITraining.jobs' guide to AI rater jobs, which we maintain, covers what this kind of rating work pays and how to start.

The size you get, and which images it suits

The result comes in one of two sizes, depending on what you upload. An image of up to about a third of a megapixel (roughly 640 x 512 pixels or smaller), such as a 200-pixel avatar or a 400-pixel supplier photo, comes back at about one megapixel: around 1024 x 1024 pixels for a square. Anything larger comes back at about four megapixels, around 2048 x 2048 for a square. In our own test a 1000 x 625 image came back at 2612 x 1632. Other shapes keep their proportions at a similar pixel total.

It is not a way to make large photos larger. Before upload, the app scales anything above about 1.2 megapixels (or 1600 pixels on a side) down in your browser, so a 12-megapixel phone photo comes back at about four megapixels, smaller than it was. Four megapixels is more than a 1080p screen shows (1920 x 1080, about 2.1 megapixels), but it is about half of 4K (3840 x 2160, about 8.3 megapixels) and far short of poster and large print sizes.

As a rule of thumb, if the longer side is under about 1800 pixels, you will get a bigger image back. To check the size of yours:

• Windows: right-click the file, choose Properties, then open the Details tab.
• Mac: open the file in Preview, then choose Tools, then Show Inspector.
• Phone: open the photo, then swipe up or tap its info button.