Let’s take a step back and understand what we just did: we’ve basically asked Preview to keep the same amount of pixels in the picture, while reducing its size by almost 50%. When we prevent Preview from resampling the image, the resolution increases dramatically when downsizing an image Let’s resize the image from the current 55×83 inches dimensions into 30×34 inches. This is understandable because this option changes the number of pixels, which is exactly what we don’t want to do since we’ve unchecked the option to resample images. Let’s uncheck the box on the previous example to see how it works.įirst you’ll notice that you can no longer resize the image according to Pixels. Resampling an image means changing the number of pixels in the image as you resize it. What does the Resample image option do in Preview? What is resampling? Changing the image type (PNG, JPEG, HEIC, PDF, etc…) would require an extra step.

The final image size can differ quite a lot compared to the original one.

Resulting size gives an idea about the file size of the resized image.

Free pre-built app: no installation is required.This is how you batch resize images on a a Mac with Preview Finally, if you have precise dimensions you’d like your pictures to be resized to, you could enter specific values for the number of pixels, centimeters or millimeters of the final image.Alternatively if you’d like to reduce the size of your images by 50%, you’d need to select per cent in the drop down menu next to Width and Height, and replace the default percentage (100%) by the the percentage value (50%) you’d like the final image to be reduced to.To make it quick, use the first drop down menu (“ Fit into”) to choose one of the default image sizes and click on “ Ok” to resize your images to the selected dimensions (for ex: 640×640).Finally, open Tools > Adjust Size… and proceed to resizing those pictures using the same process as we described in previous paragraphs. Now, in order to resize those images in one shot, you’ll need to select them all by going to Edit > Select All in the menu bar.ģ. If that’s not the case, select View > Thumbnails in the menu bar. Preview will now open and all the images you’ve previously selected should be visible in the left sidebar. Once you have selected all the images you’d like to resize, right click and select Open With > PreviewĢ. Click on your Mac’s Finder app and open the folder that contains all the images you want to resize at the same time, select all those image files by clicking on them while holding the Shift key.

How to change a photo size on mac