I have 3 images of plant germination and each image is of different dimensions. I resized all of them using paint to 600 (width) X 450 (length) pixels. But the scale size in the 3 images is of different length. I drew 4 cm scale by image j in all 3 images but their length is varying on all of them. So, How should equalize scale lengths in the all 3 images, so that its easy to compare shoot length among them ?
Hi Govind,
You can use ImageJ software to compare the distance between pixels and convert it to centimetres or millimetres. The only thing you'll need is a ruler at the bottom of the photo.
Hi Govind Mahendra Singh,
There are probably many ways, but I would first set the scale for each image in ImageJ, then crop them to the same "real world" dimensions. Here's how that might work:
- I assume you have a "true" scale measurement for each image, e.g. a ruler in as close to the same focal plane as your subject seedlings as possible.
- One at a time, take each image in ImageJ or FIJI, draw a line from end to end of your ruler or subdivision of your ruler, and set the scale for that image (Analyze -> Set Scale...). Now ImageJ knows how many pixels in this image equals some real-world length.
- I'm assuming you want to end up with three pictures (rectangles) side by side of the same size on the page, and are also of the same scale so if you were to draw a scale bar on each image, they would be the same apparent size on the page.
- Start with the image with the biggest seedlings. In ImageJ, draw a rectangle around your seedling(s) that you want to roughly end up in your eventual pictures. Go to Edit -> Selection -> Specify. Check the box for Scaled Units (units). Now the height and width of the box you drew should be shown in "real world" units. You might want to round to some nearest convenient size (e.g. 2 cm by 4 cm). Crop the image (of course, save an original copy somewhere else first).
- Repeat the above with your other two images, but draw a rectangle of the same "real world" size as your first image. Go to Specify again, and manually enter exactly the same dimensions as your first image. Crop. They should now all be the same relative dimensions, and of equal scale. However, they will be different pixel dimensions, so you may notice some pixelation in some if you had to "zoom in" too much.
- You should double check this procedure in case my reasoning or instructions were wrong by drawing a scale bar in ImageJ on each of your scaled images, making the scale bars the same real world size. They should be the same size on the page in the final product. Often, for the final presentation, you can just have one scale bar in one image, and say in the legend that the scale bar applies to several images so your figure isn't cluttered up.
- You can now import these images to some design software like Illustrator or Powerpoint. They may appear as different sizes on the page at first, but since you now know that each image is the same "real world" dimensions, you can click and drag the corners until they are the same apparent size on the page. I would avoid resizing to the same pixel dimensions, unless there's some compelling reason to do so.
Good luck, and I hope that works for you!
Chris
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