PNG, SVG and DPI Explained for Stamps
When you finish designing a stamp or seal, the last step is exporting it as a file, and that choice matters more than most people expect. Pick the wrong format and your crisp circular seal turns into a blurry blob on a printed invoice, or a stamp manufacturer emails back asking for "vector artwork." This guide explains the three things that decide how good your stamp looks: raster versus vector formats, transparency, and DPI. It also tells you which Stampzio export option to choose for the web, for documents, and for professional printing.
Raster vs Vector: The Core Difference
Every digital image is either raster or vector, and understanding the split solves most format confusion. A raster image is a grid of colored pixels, like a mosaic. PNG, JPG, and GIF are all raster formats. A raster stamp looks great at the size it was created, but if you enlarge it, the software has to invent new pixels by guessing. The result is soft, jagged edges, an effect called pixelation. Zoom into a low-resolution stamp and you see stair-stepped curves and fuzzy text.
A vector image stores your design as mathematical instructions: "draw a circle of this radius, place this text along this arc, fill this shape with this color." SVG is the common vector format. Because it is described by math rather than fixed pixels, a vector stamp can be scaled to any size, from a tiny web icon to a giant banner, and stay perfectly sharp at every zoom level.
Rule of thumb: raster is fixed-resolution and best for finished images at a known size; vector is resolution-independent and best for anything that may be resized or professionally printed.
Why PNG Transparency Matters for Stamps
A stamp is almost never a solid rectangle. It is a circle, oval, or badge shape with empty space around it and often inside it. Export that stamp with a white background, and dropping it onto a colored document or a photo leaves an ugly white box around your seal.
PNG solves this with an alpha channel, a hidden layer that records how transparent each pixel is. Where your stamp has no ink, the pixels are fully transparent, so only the rings, text, and graphics show. This is why a transparent PNG can sit naturally over any background, exactly like a real rubber stamp pressed onto a page.
JPG cannot do this. It has no transparency support and uses lossy compression that adds blur and colored artifacts around sharp edges, the worst case for the crisp lines of a stamp. Avoid JPG for stamps entirely. In the Stampzio editor, when you export a transparent PNG the background is removed automatically, so your seal is ready to place anywhere.
SVG: Infinite Scalability
SVG (Scalable Vector Graphics) is the vector option. An SVG stamp is a small text-based file that browsers, design tools, and many print workflows can read directly. Its advantages are specific and real:
- Any size, always sharp: the same file works as a 32-pixel favicon or a poster-sized graphic with zero quality loss.
- Tiny file size: a simple seal is often just a few kilobytes, far smaller than a high-resolution PNG.
- Editable: colors, text, and shapes remain individual objects, so a designer or manufacturer can adjust them.
- Print-friendly: because there is no fixed resolution, DPI is never a concern.
SVG has natural transparency too, so there is no background to remove. Its main limitation is that some office documents and email clients do not accept SVG directly, where PNG is more universally supported. That is why Stampzio offers both.
What DPI and Resolution Actually Mean
DPI stands for dots per inch and describes how many pixels are packed into each inch of a printed image. A closely related term, PPI (pixels per inch), refers to the on-screen version of the same idea. The higher the number, the more detail per inch, and the sharper the print.
Here is the key insight: a raster image has a fixed number of pixels. A 900-pixel-wide stamp is always 900 pixels wide. DPI simply decides how those pixels are spread out when printed:
- At 72 DPI, those 900 pixels span 12.5 inches, so each pixel is large and visible. Fine for screens, terrible for print.
- At 300 DPI, those same 900 pixels span just 3 inches, so pixels are too small for the eye to detect. The print looks smooth and professional.
So DPI is really a relationship between pixel count and print size. To print a stamp sharply at a given physical size, you need enough pixels to hit 300 DPI at that size.
Why 300+ DPI Is the Print Standard
At normal reading distance, the human eye stops distinguishing individual dots at roughly 300 DPI. That is why 300 DPI is the accepted minimum for crisp printed material such as documents, business cards, and packaging. Below it, text softens and print shops routinely reject the artwork. To find the pixels you need, multiply the print size in inches by 300: a stamp printed 1.5 inches wide needs about 450 pixels; at 2 inches, about 600 pixels.
Format Comparison at a Glance
| Property | PNG (raster) | SVG (vector) | JPG (raster) |
|---|---|---|---|
| Transparency | Yes (alpha channel) | Yes (built in) | No |
| Scales without quality loss | No | Yes, infinitely | No |
| DPI matters? | Yes | No | Yes |
| Edges on sharp lines | Clean | Perfect | Blurry artifacts |
| Typical file size | Medium to large | Very small | Small |
| Best use | Documents, web, email | Print, resizing, editing | Avoid for stamps |
Which Stampzio Export Should You Choose?
The right file depends entirely on where the stamp will end up. Here is a simple decision guide.
- For websites and email signatures: export a transparent PNG. It displays reliably in every browser and email client and keeps its transparent background. A moderate resolution keeps the file light and fast to load.
- For Word, PDF, and other documents: export a transparent PNG at a higher resolution. This drops cleanly over signatures and letterheads, and if the document is later printed, the extra pixels ensure it still looks sharp.
- For professional printing or a stamp manufacturer: export an SVG whenever possible. Vector artwork is what stamp makers, engravers, and print shops prefer, because they can scale it to the exact die size with no quality loss. If a supplier only accepts raster files, send the highest-resolution PNG available so it clears the 300 DPI bar at the physical stamp size.
Quick answer for manufacturers: give them SVG first. If they insist on a raster file, send a large transparent PNG, never a JPG.
You can set your shape, rings, and text in the Shape tab of the Stampzio editor, then export a transparent PNG or SVG in a couple of clicks. When in doubt, keep both on hand: the PNG covers everyday digital use, and the SVG guarantees a flawless result at any size a printer might ask for.