Image Size and Canvas Size in Paint by Zaweba
Resize pictures in Paint by Zaweba with Image Size and its resampling methods, including Preserve details and Pixel art, and add space with Canvas Size.
Two of the most used commands in any editor sound alike and do quite different things. Image Size changes how many pixels a picture has, scaling everything in it. Canvas Size changes the area of the document, adding or cutting space round the edges without scaling anything. Paint by Zaweba puts them side by side, and knowing which is which saves a lot of confusion.
Image Size
Image Size, on Ctrl+Alt+I, resamples the picture: it works out new pixels at the new size. Use it to make a large camera photo small enough for email or the web, to set a picture to an exact pixel width for a website, or to change the resolution for print.
The way new pixels are calculated is the resampling method, and the choice matters.
Smooth and bilinear are general purpose methods that give soft, even results. Hard-edged keeps edges sharp without blending, which suits screenshots and graphics with hard lines. Lanczos-3 is a high quality method that keeps fine detail well, a strong choice for photos. Mitchell is another quality method, often a little softer.
Preserve details is meant for enlarging photos. It combines denoising, Lanczos scaling and edge-following sharpening, so the picture gets bigger without looking as mushy as a plain upscale.
Pixel art uses Scale2x and Scale3x, methods designed for pixel graphics. They double or triple the size while keeping the crisp, blocky character and smoothing diagonal steps in a way that suits the style.
Shapes and text stay sharp
When you use Image Size, shapes and text scale as vectors. They are recalculated at the new size, not resampled as pixels, so they stay perfectly sharp whether you make the document bigger or smaller.
Canvas Size
Canvas Size, on Ctrl+Alt+C, changes the size of the document without scaling the picture. Make the canvas bigger and you get new space round the picture. Make it smaller and the edges are cut off.
Two settings control where the change happens. The anchor says which part of the picture stays put. Anchor in the centre and space is added evenly all round; anchor at the top and space is added at the bottom. The fill sets what colour the new space gets.
Jobs for each
Image Size: preparing photos for the web, making thumbnails, enlarging a small picture for print, scaling pixel art up for display.
Canvas Size: adding a white border for a print, adding a strip at the bottom for a caption, making a picture square for a social post by adding space at the sides, or making room to extend a background.
Avoiding quality loss
Resample as few times as possible. Every resize recalculates pixels, and repeated resizing softens a picture. Keep the full size original and make smaller copies from it, rather than shrinking a copy again and again. When enlarging photos, use Preserve details. When enlarging pixel art, use the Pixel art method. When shrinking photos, Lanczos-3 is a safe default.
The two mixed up
Using Image Size when you wanted Canvas Size, so a picture is stretched instead of getting a border. Using Canvas Size to make a picture smaller and cutting off part of it. Forgetting to keep proportions in Image Size and squashing the picture. And expecting enlargement to add real detail; it can look cleaner, but it cannot invent what the camera never caught.
Once the difference is clear, these two commands handle nearly every sizing job you will meet in Paint by Zaweba.
