Vector vs raster graphics: what it is and what it is for

1What is the difference between vector and raster?

A bitmap image, also called raster, is a grid of tiny colored squares called pixels. A photo from your phone is an example: thousands of pixels, each with its own color, that together form the scene. The more pixels, the more detail, but also the larger the file.

A vector image doesn't store pixels but instructions: draw a line from here to there, a curve with this radius, fill this shape with this color. When displaying it, the program calculates the drawing for the size it needs. That is why a vector logo can fit on a business card or a billboard without losing definition.

2What happens when you enlarge each type?

If you enlarge a raster, the program has to invent pixels that didn't exist, and the result is a blurry image with jagged edges. That is the source of the classic problem of a logo that looks fine on the web but terrible on a banner. The real fix is to start from a higher-resolution file, not to stretch the small one.

A vector, on the other hand, is recalculated at every size, so its edges stay clean. Its limit is different: it isn't suited to representing complex photographic scenes, because describing millions of color variations with shapes would be impractical.

3Common formats of each type

Rasters include JPG, ideal for photos with lossy compression; PNG, which supports transparency and is good for screenshots and graphics with sharp edges; WebP, designed for the web; GIF, with simple animations; BMP, uncompressed; and TIFF, common in scanning and printing. The best-known vector format on the web is SVG.

PDF is a special container: it can include vector text and drawings together with raster images on the same page. A contract exported from a word processor is usually almost all vector and text; a scanned document is one raster image per page.

• Photos and screenshots: JPG, PNG or WebP.
• Logos, icons and illustrations: SVG or vector PDF.
• Scans: raster, usually JPG or TIFF inside a PDF.
• Blueprints and diagrams: best kept as vector.

4When to use each one

Use raster for photographs, screenshots and any image with complex gradients. Use vector for brand identity, icons, simple maps and pieces that will be printed at very different sizes. If you receive a logo only as a small JPG, always ask the designer for the vector version.

A common mistake is believing that saving a JPG inside a PDF makes it vector. It doesn't: the PDF only carries it; the pixels are still pixels. Another myth is that a PDF always preserves quality; it depends on how the images it contains were created and compressed.

An easy rule to remember: if your image is a real scene or has many subtle tones, it is raster; if it is made of clean shapes and flat colors, it should probably exist as a vector. Keeping both versions of your important graphics will save you a lot of trouble later.

5Rasterizing: turning a page into an image

Rasterizing means going from vector to pixels. When you convert a PDF page into an image, the text and drawings become pixels at a given resolution. It is useful for sharing a page as a photo, posting on social media or making sure it looks the same everywhere, but it has costs: the text is no longer selectable and the image doesn't enlarge well beyond its resolution.

Going back from pixels to vector is neither automatic nor perfect. Although vectorization tools exist, the result is an approximation, and OCR only recovers text, not the exact shape of the drawings.

6Vectors, pixels and Rayo PDF GO

With PDF to images you convert pages into raster files; with Images to PDF you do the opposite, gathering photos or screenshots into one document. It pays to choose the resolution for the destination: higher for printing, lower for screen. If you need to cut the size, Compress PDF and Compress image reduce it at the cost of some detail.

Other tools like Resize image, Crop image and Rotate image work on pixels. Rayo PDF GO does not convert raster to vector; if you need an editable logo, start from the original design file. All processing happens on your device.