How to Resize a Photo on Mac: A Comprehensive Guide

Post-processing is a crucial step in photography. Even with careful composition and shooting, you might still need to make adjustments to your photos after taking them. This isn’t just about color correction or exposure fixes; sometimes, even a simple task like resizing your image is necessary.

Understanding Photo Resizing on Mac

When you think about how to resize a photo on Mac, it’s important to understand what resizing can entail. Resizing isn’t just one action; it can mean different things depending on your goal. You might want to physically change the dimensions of your photo, which can involve cropping or enlarging it. Alternatively, you might need to reduce the file size of your image without altering its aspect ratio or field of view. This is often achieved by changing the image resolution. Reducing file size is particularly important for online sharing, as many social media platforms have limitations on the file size of uploaded images.

Let’s explore the various methods for image resizing on macOS, covering both dimension adjustments and file size reduction.

Resizing Image Dimensions Using Preview on Mac

The simplest way to change the dimensions of a photo is by using the built-in Preview app on your Mac. Here’s a step-by-step guide:

1. Open with Preview: Locate the image you want to resize and open it with the Preview application. Preview is the default image viewer on macOS.

2. Access Adjust Size: In the Preview menu bar, click on “Tools” and then select “Adjust Size…”. This will open the “Adjust Size” window.

3. Enter New Dimensions: In the “Adjust Size” window, you can enter your desired new dimensions for the width and height of the image. You can input specific pixel values or use percentages.

4. Resize Options: Preview offers several options to control how your image is resized:

   • Resize by Percentage: To resize by a percentage, select “percent” from the dropdown menu next to the Width and Height fields. Then, enter the percentage by which you want to increase or decrease the image size. For instance, entering 50% will reduce the image to half its original size.
   • Maintain Proportions: To keep the original aspect ratio of your image, ensure the “Scale proportionally” checkbox is selected. When this is checked, changing either the width or height will automatically adjust the other dimension to maintain the correct proportions, preventing distortion.
   • Resampling and Detail Preservation: The “Resample image” option is crucial. If you want to change the dimensions without altering the number of pixels (and potentially losing detail when enlarging), deselect “Resample image” before adjusting the width or height. However, for most resizing tasks, especially when reducing size, leaving “Resample image” selected is appropriate as it recalculates the pixels for the new dimensions.

5. Confirm Changes: Once you have entered your desired dimensions and chosen your options, click “OK” to apply the resizing.

6. Save Your Resized Image: To save the resized image, go to “File” and select “Export…”. Choose a new name and location to save the resized image, preserving your original file. You can also choose different formats like JPEG, PNG, or TIFF during export.

Cropping Photos in Preview to Resize

Cropping is another effective method to resize a photo on Mac, primarily to reduce its dimensions and file size by removing unwanted areas. Preview also provides a straightforward cropping tool:

1. Open Image in Preview: Open the photo you wish to crop in the Preview app.
2. Show Markup Toolbar: Click the “Show Markup Toolbar” button, which looks like a toolbox icon, located in the Preview window.
3. Select the Crop Tool: In the Markup Toolbar, click on the “Select” tool (the rectangular selection icon).
4. Define Crop Area: Click and drag on the image to draw a rectangular selection over the area you want to keep. Adjust the selection handles to fine-tune the crop area.
5. Crop the Image: Once you are satisfied with your selection, click the “Crop” button in the Markup Toolbar (it looks like a rectangle being trimmed). This will remove the areas outside your selection, effectively cropping the image.
6. Save the Cropped Image: Similar to resizing, go to “File” > “Export…” to save the cropped image with a new name and location.

How to Resize a PDF Image on Mac using Preview

You can also resize images embedded within PDF documents using Preview:

1. Open PDF in Preview: Open the PDF file containing the image you want to resize with Preview.
2. Select Export as PDF: Go to “File” in the menu and choose “Export as PDF…”.
3. Quartz Filter Option: In the export dialog, click on the “Quartz Filter” dropdown menu.
4. Choose Reduce File Size: Select “Reduce File Size” from the Quartz Filter options. This built-in filter will automatically reduce the image resolution within the PDF, thus resizing the image and reducing the overall PDF file size.
5. Save the Resized PDF: Choose a name and location and click “Save” to export the resized PDF.

For more precise control over PDF image resizing, or to enlarge images in PDFs, you might need dedicated PDF editing software like Adobe Acrobat Pro, which offers more advanced image manipulation options within PDFs.

Enlarging Images on Mac with Luminar Neo

While Preview is excellent for basic resizing and cropping, if you need to enlarge photos on Mac and maintain or even enhance image quality, specialized software like Luminar Neo is recommended. Luminar Neo utilizes AI-powered tools to intelligently upscale images with minimal quality loss.

Here’s how to enlarge images using Luminar Neo:

1. Open Image in Luminar Neo: Launch Luminar Neo and open the image you want to enlarge in its catalog.
2. Export for Resizing: Select the image and go to “File” > “Export”.
3. Resize Options in Export: In the Export dialog, you’ll find a “Resize” dropdown menu. Choose “Long Edge”.
4. Enter Desired Size: Enter the desired length for the longer edge of your image in pixels. Luminar Neo will automatically calculate the other dimension to maintain aspect ratio.
5. Choose Format and Quality: Select your desired image format (JPEG, TIFF, PNG, etc.) and adjust quality settings if applicable.
6. Save Enlarged Image: Click “Save”. Luminar Neo will use its advanced resampling algorithms to enlarge the image to your specified dimensions, attempting to preserve detail and minimize pixelation.

Luminar Neo’s advantage lies in its sophisticated resampling methods, which are designed to produce better results when enlarging images compared to basic resizing tools. It offers a balance between increasing size and maintaining visual quality.

Reducing File Size for Web Using Preview

If your primary goal is to reduce the file size of a photo for web use or email, Preview can efficiently handle this as well:

1. Open with Preview: Open your image in the Preview application.
2. Adjust Size with Resampling: Go to “Tools” > “Adjust Size…”. Ensure “Resample image” is checked.
3. Reduce Resolution: In the “Resolution” field, enter a lower value. The standard resolution for web images is 72 pixels per inch (PPI). Reducing the resolution effectively decreases the file size.
4. Observe New Size: Preview will display the new file size at the bottom of the “Adjust Size” window, allowing you to see the impact of your resolution adjustments.
5. Save for Web: Export the image (“File” > “Export…”) and consider using JPEG format with a lower quality setting to further reduce file size if needed, balancing file size with acceptable image quality for web display.

Resizing Images Without Losing Quality

To resize photos on Mac while minimizing quality loss, especially when reducing dimensions, follow these best practices using Preview:

• Reduce Size, Don’t Enlarge: It’s always better to reduce the size of a larger image than to enlarge a smaller one. Enlarging often introduces pixelation and blur.
• Gentle Resizing: When using “Adjust Size”, make gradual reductions rather than drastic changes in dimensions in a single step.
• Use Appropriate Format: For web use, JPEG is usually a good balance of file size and quality. For archival or further editing, TIFF or PNG might be preferable to retain maximum quality, although they result in larger file sizes.

For scenarios where quality is paramount, especially when enlarging, investing in professional software like Luminar Neo, with its advanced resizing algorithms, can make a significant difference in the final output quality.

Batch Resizing Multiple Images on Mac with Preview

Preview also supports batch processing, allowing you to resize multiple images at once:

1. Select Images in Finder: In Finder, select all the images you want to resize.
2. Open with Preview: Right-click on the selected images, choose “Open With”, and select “Preview”.
3. Select All Thumbnails in Preview: In Preview, you will see one image in the main window and thumbnails of the rest in the sidebar. Press “Command + A” to select all thumbnails.
4. Adjust Size for All: Go to “Tools” > “Adjust Size…”. Make your resizing adjustments in the “Adjust Size” window as described earlier.
5. Apply to All: Click “OK”. The resizing settings will be applied to all selected images.
6. Save Resized Images: Go to “File” > “Export Selected Images…”. Choose a location to save the batch of resized images. Each image will be resized according to your settings.

Conclusion

Knowing how to resize a photo on Mac is a fundamental skill for anyone working with digital images. Whether you need to adjust dimensions for printing, reduce file size for web sharing, or enlarge images while preserving quality, macOS offers several effective methods. From the simplicity of Preview for basic tasks to the advanced capabilities of Luminar Neo for more demanding resizing needs, you have a range of tools at your disposal to manage your image sizes efficiently. By understanding these techniques, you can optimize your photos for any purpose, ensuring they look their best and are perfectly sized for your intended use.

Luminar Neo photo editing software for Mac shown on a laptop