Images, both printed and on-screen, are created from an array of coloured ‘dots’ (the exact dot shape depends on the technology).

These two images are both being displayed at the same size. They don't look especially different, do they?

Source image is 500px wide

Source image is 250px wide

But if we blow them up to twice the size, we start to see a problem with one of the two images...

Source image is 500px wide

Source image is 250px wide

The second image has less pixels (px) than the first. Pixels are squares of colour that make up the image. The first image is 500 pixels wide and 282 pixels tall (a total of 141,000 pixels), while the second is 250x141 (35,250 pixels in total). So while we might say it's half the size in terms of its width and height, it only has a quarter of the number of pixels within it: the larger image has four times the amount of data than the smaller one.

Here's a close-up of the rabbit's eye from those two testcards:

250px image:
The eye is 6px square
(36 pixels)

500px image:
The eye is 12px square
(144 pixels)

120x120px
image

Of the above bright eyes, the first eye is the actual 6px image (12px in the second example) blown up to 120px in your browser. The blurriness you might see is your browser compensating and applying something called 'anti-aliasing' to blend the pixels together at the new scale. The second image is a simulation of what the original image actually looks like if you were to zoom in. For comparison there's also a 120x120px 'full-size' image of the eye.

You can find the dimensions of an image in its properties:

Screen use

As monitors get bigger and bigger, so the number of pixels that makes up your screen increases. Most of the monitors on campus are (at the time of writing, at least) 1920x1080px, which means that the 500px-wide images above would take up about a quarter of the screen width when displayed at actual size.

A 500px-wide image looking good on a 1920x1080px display.
Why not open the image in a new tab and see how it looks on your display?

The widescreen monitors on campus are generally 22" screens, so (when measured with a ruler) they have a physical width of 47.3 cm. That means there's roughly 41 pixels per cm (1920 ÷ 47.3).

By that reckoning, the 500px image on my screen could be just over 12 cm wide without losing quality.

Print use

With print it's a different matter: you need a higher resolution. There's an old printer's rule that for an image to look good in print it should be about 300 dots (of ink) per inch (300 dpi). A younger printer would convert that to about 120 pixels per centimetre. Again, there's a bit of leeway, but using this rule a 500px image shouldn't take up much more than 4 cm on your page (500 ÷ 120 = 4.17):

A 500px-wide image looking good at 4.17cm wide on an A4 sheet.
You'd need a 2520px-wide image to fill the width of the sheet to a decent standard.

What's this mean for our posters?

It means we have to do some sums to make sure our images are of an appropriate size to look good when printed. Let's take a couple of examples:

You can get away with an image that's slightly smaller if necessary. And if you're using a background image that takes up the whole of your page, then for an A1 poster that's going to have to be 10,000 pixels on its long side which may be tricky to source. If it's in the background, it's probably not quite so important that the resolution is perfect, but try to get as close as possible.

We've established, then, that a photographic image should be at least a certain number of pixels wide and tall, corresponding to the physical size it will be printed at. When you're sourcing an image, find one that's big enough to print at a decent standard.

Of course, the bigger an image is physically, the more room it tends to take up on the computer and in the memory. It's therefore also a good idea not to go too over the top: don't use an image that's massively bigger than your printing needs. If your image just needs to be 1800px wide, using something twice that size is a waste of memory. And posters are big things; the more you put on the page, the slower PowerPoint will get, and the more at risk it will be of crashing. Try to find an image that's a good match for the size you require.

If your image is much too large (and it might be, especially if you've taken it on a digital camera or your phone), you should consider resampling that image using an image editor. Here are some options:

Re-scaling in Corel PHOTO-PAINT

Corel PHOTO-PAINT, part of the CorelDRAW graphics suite available on University computers, can be used to resize images. The re-sizing dialogue lets you choose the resolution and dimensions, and can adjust the pixel dimensions accordingly using print dimensions.

1. Open the image in Photo-Paint, then go to Image > Resample to open the 'Resample' dialogue:

2. Either:
   1. Set the dpi (dots per inch) "Resolution" values to 300, and then set the "Image size" width and height to the size you want, or...
   2. Switch the "Image size" units to pixels and enter the desired width and height;
3. Hit OK
4. Save your resampled image (use Save As... if you want to save a new copy rather than overwriting the original, and choose an appropriate filetype, e.g. jpg or png).

Re-scaling in PIXLR

PIXLR is a free-to-use online editor, so needs no download/install. It re-sizes the pixel dimensions, so you need to calculate these yourself first for the size of image you want on the page.

1. Open the 'PIXLR X' editor and choose Open Image to open an image from your computer
2. From the side menu, choose Properties > Resize Image to open the 'Resize Image' dialogue
3. Enter the pixel dimensions you need ('Constrain proportions' will ensure both dimensions change accordingly)
4. Hit Apply
5. Save your image (give it a new name if you don't want to overwrite the original, and choose an appropriate filetype, e.g. jpg or png).

Resampling up

It's theoretically possible to resample an image upwards in resolution. When you stretch an image in PowerPoint, this is what you're doing. But there's no magic at play; pixels will just get doubled up, and the quality won't be very good (take the rabbit example from earlier, for instance). You can get away with a little bit of enlargement but not very much.

If you've done your sums right, the image should give the correct resolution if you adjust it to the size you planned. You should be able to drag by any of the four corner 'handles' to resize — don't use the side handles as this will squash or stretch the image.

To set a precise size, enter the dimensions as numbers. If you set the width, the height should adjust to retain the proportions:

If your image isn't resizing proportionally, you can force it to "Lock aspect ratio" from the "Format Picture" side-menu, which can be accessed from the image's right-click menu, or from the toggle at the bottom om the Size ribbon group.

To focus on what's important, it's a good idea to crop close in to the main subject of the picture, and you do this using the cropping tool:

1. Select the image and choose Picture Tools > Format > Size > Crop (or Picture Format > Size > Crop on a Mac)
2. Using the handles on the edges, drag to indicate the image area you want to be visible:

Original image

Cropping

Cropped & resized

After you've finished cropping, you may want to resize the image again.

The Picture Format ribbon has a number of additional toys to play with, particularly the ones in the Adjust group. For instance:

Transparency options

There are a couple of tools in PowerPoint which will let you make sections of your image transparent: a process called isolation.

You can find isolated images online (they're typically PNG format), and you can isolate images in dedicated graphics programs too, but PowerPoint has these basic options built in.

For simpler images or single-colour backgrounds, use Color > Set Transparent Color..., otherwise try Remove Background: you paint out the sections you don't want and they get removed (though the edges can be a bit blotchy).

There's also Transparency, which lets you adjust the opacity of your image as a whole.

Other adjustment settings

You can make corrections to the colour, contrast, sharpness and brightness of your image, and there's also a selection of Artistic Effects you can apply. Some of these effects can look a bit naff, but others are actually quite effective. They can also be useful for making an under-resolution image look presentable. For example, the 'Create & Communicate' icon from our Skills Guides is only 125px wide: fine for a website, but it could take up only a centimetre or so on a poster without starting to look blotchy (as it does here at three times the size). By copying and pasting as a new image at the new size, and then applying effects, this blotchiness can be disguised to some extent:

Picture effects

The Picture Styles ribbon group has some pre-programmed effects such as shadows and borders. More of these effects (and further settings) can be found at Picture Format > Picture Styles > Picture Effects. You can also rotate or flip an image with the options in the Arrange group: sometimes a jaunty angle can make all the difference!

There are plenty of applications for creating diagrams and charts. Take a look at our Data visualisation Skills Guide for some suggestions.

When exporting from another application, there are two filetypes to consider:

PNG

Portable Network Graphics (.png) images have a better image quality than a JPG because they use lossless compression. Never use a JPG for a diagram unless you absolutely have to: it will not give crisp lines. But a PNG will. What's more, parts of a PNG image can be 'isolated': in other words, parts of the image can be transparent (or even semi-transparent) — something which has its uses for images generally, but can be especially useful with diagrams.

With a PNG, you'll need to ensure that your image has sufficient resolution for the size it's meant to be on paper.

SVG

All the images we've looked at so far have been made up of pixels. But that's not the only type of digital image. Simple images and diagrams can also be created using vectors. These vector images are essentially made up from points, lines and curves using a set of geometric instructions. And because they're constructed from geometric instructions they have the advantage of being scalable to any size without distortion.

The most common vector files are Scalable Vector Graphics (.svg). These can be imported into PowerPoint, and can often even be converted to PowerPoint shapes, which can then be deconstructed, recoloured, etc, as well as resized without loss of quality (all that dots per inch stuff becomes irrelevant!). For this reason, SVG is by far the best filetype to use for comparatively simple diagrams.

Copying and pasting

Copying and pasting an image into PowerPoint is always an option, though pay attention to the quality of what gets pasted (before doing anything with the image, try right-clicking it in PowerPoint and choosing Save as Picture... to save a copy to a folder and see what the pasted image's resolution is). If you try a 'copy and paste' and it seems to work, make sure you also save the diagram in the other application so you can edit and re-insert it if necessary.

Spreadsheet applications can produce good quality charts and graphs — take a look at our Essential Spreadsheets guidance for more details. Charts in Google Sheets, for instance, can be downloaded as SVG or PNG files from the Download option on the three-dot menu (⋮).

By virtue of them both being part of Microsoft's Office suite, Excel has some additional options in terms of its interoperability with PowerPoint.

There are essentially three ways by which you can paste an Excel chart into PowerPoint:

If you are using the "Linked" option, any edits to the linked Excel file will automatically be reflected in the document. But a linked or embedded chart can also be edited from within PowerPoint:

1. Select the chart, right-click and choose Edit Data (or go to Chart Design > Data > Edit Data) — there are sub-menu options to Edit Data using a mini-window in the document or to Edit Data in Excel;


2. After making changes, simply close the spreadsheet window; with linked charts you can continue to work with both open.

The drawing tools in PowerPoint are great for diagrams and flowcharts, but make sure you make good use of the various sizing and alignment tools:

• ‘Smart’ guides show when objects line up or centre
• When selecting several objects (which you can do by dragging around them or by holding down the shift key), use the alignment controls to line things up or space them evenly
• Each new object you draw is placed on a 'layer' above any others, but with Bring Forward/To Front and Send Backward/To Back you can change the stacking order; there's also Home > Select > Selection Pane... (or Shape Format > Arrange > Selection Pane on a Mac).
• Precise alignment and even distribution of several shapes can be achieved using Align... and Distribute...
• The connection shapes (lines) are designed to latch on to specific anchor points on shapes, and the connections will remain even when you move shapes about:

SmartArt

PowerPoint also includes a feature called SmartArt with which you can create different types of diagram from a gallery of options. The content is entered using a bulleted list, and colours etc are chosen from palettes.

It's quite flexible, but you need to choose the appearance carefully to ensure you preserve consistency with other content (and to help your design stand out).

Drawing tools

Some basic principles apply within PowerPoint:

• drawings and diagrams are composed of shapes and lines, each being a separate object on the page (although these objects can be grouped to behave as one)
• shapes can have a fill, which may be solid colour, graduated colour, an image, or a pattern, with varying degrees of transparency
• shapes may have an outline, which can be in a range of colours, thicknesses and patterns (e.g. dashed or dotted); lines consist entirely of this outline property
• shapes may contain text (we'll get to that...)
• all objects have a stacking order – one in front of another – which you can change to get the result you want
• any object can also have effects applied, including shadows, glowing and soft edges, and reflections.

To draw a shape or line in PowerPoint:

1. Choose Insert > Illustrations > Shapes and select the shape or line you need
2. In most cases, drag to draw the shape/line
3. For lines with more complex shapes, you may need to click several times to place 'anchor' points, and double-click to finish.

Hold down shift while dragging to draw squares and circles rather than rectangles and ellipses;
For perfectly horizontal/vertical lines, hold down shift after you've started holding down the mouse button.