Use these tips to get high resolution images:
PowerPoint (modify to get 300 dpi)
- Problem: PowerPoint slides export at 72 dpi (low resolution) by default. The maximum is 150 dpi by adjusting settings within the program. It's not good enough for publication.
- How to get 300 dpi for images: Change the computer's registry settings for PowerPoint to increase resolution further. Carefully follow these instructions from the official Microsoft website to increase the maximum export resolution to 300 dpi. Export slides as images by using "Save As" and selecting .tif file format.
- How to get >300 dpi for line art: copy/paste line art from PowerPoint into a vector program like Inkscape for high resolution. Save the Inkscape file as .svg or .pdf to keep the image as a vector graphics file. No blurry text when you zoom in.
- Image edits: use free IrfanView (Windows) or GIMP (cross-platform) image software to crop out white space and re-save as an LZW-compressed .tiff image. LZW compression reduces the file size while keeping the image publication quality.
- How to get >300 dpi for pdfs:
- For conference posters created as one large slide, exporting a ppt to pdf will result in blurry images and text. I prefer to use online converters. Example: http://www.zamzar.com/convert/ppt-to-pdf/
R code (>300 dpi)
- If making a plot with R, add res=1200, compression='lzw' to the tiff image function for a 1200 dpi image with a reasonable file size. Saving as a .png image will result in a smaller file size than .tiff, but many journals prefer .tiff.
- Use R package cowplot to arrange multiple figures.
- See tips for aligning different axes with cowplot and ggtree.
- See tips for aligning shared axes:
- Comparing cowplot, egg, and patchwork R packages
- Compare cowplot, ggpubr, and gridExtra
- cowplot is best for aligning figures using the same axis
- Use R package pdftools to merge multiple pdf files into a multi-page pdf.
- Great for creating high resolution supplemental files for publication.
Vector software, e.g. Inkscape (>300 dpi)
Most journals want line art at 600-1200 dpi resolution. PowerPoint doesn't go this high, but you can work around this by pasting your PowerPoint line art or Excel plots into a vector software like Inkscape (cross-platform, free) or Adobe Illustrator (not free, but a great tool if your institution has a license).
Save as a .svg or .pdf vector file and submit that to the journal. Alternatively, export a high resolution .tiff image file. Free software like Inkscape may require that you save a high resolution .png file, then convert it to .tiff with other software.
Inkscape tips for new users:
- Adjust the document size to fit journal width and height limits
- File: Document Properties: Custom Size
- Select the units, then the width and height
- Create a white box background and move it under your line art
- Create a white box and position it first. (Set fill=white, stroke=white or none)
- Object: Lower to Bottom
- Resize objects proportionally
- Object: Transform: Scale
- Check the box "scale proportionally"
- Set the units to inches and change either width or height. The other will adjust automatically.
- Save in high resolution
- File: Export Bitmap
- Save either the whole document size or just the drawing (the parts that aren't blank)
- Set the dpi resolution desired (300 for microscope images, 600 or 1200 for line art)
- Check the resulting .png image with IrfanView or another graphics software, crop out any white space you don't want, then "Save As" a .tiff image with LZW compression.
- LZW compression is required to meet file size limits for upload to the journal website, commonly < 10 MB.
Which files to use for different stages of manuscript preparation
- Vector file (.svg) = for yourself to edit
- Keep this! It's much easier to edit a vector file than a static image
- Easier to resize parts of the figure
- Easier resize/add/remove text and arrows
- Export to pdf or png from Inkscape
- pdf - can be submitted to the journal directly
- png - need to open and resave as a tiff image for journal submission
- Combined pdf file (review version, not final publication version)
- For emailing authors or reviewers, you can combine all your main figures into one pdf:
https://www.zamzar.com/convert/png-to-pdf/ - Or use R package pdftools if you are merging different pdfs
Last edited 7/3/2022
