This free online tool generates image histograms for red, green, blue, and greyscale values. Histograms can be generated for multiple images at once in batch.
You can also export the values into a csv file for further analysis in your spreadsheet application.
Note: All processing is done on the client side. That means your images are not transferred to the server.
If you you're an Android enthusiast that likes to learn more about Android internals, I highly recommend to check out my Bugjaeger app. It allows you to connect 2 Android devices through USB OTG and perform many of the tasks that are normally only accessible from a developer machine via ADB directly from your Android phone/tablet.
How This Tool Works
An image histogram displays pixel value distribution within an image.
This tool basically creates 256 bins for each color (red, green, blue) and greyscale (luma) intensity. The number of bins is shown on the horizontal axis.
The tool then loops through every image pixel and counts the occurrence of each intensity. The counts of occurrences in each bin are then displayed on vertical axis.
Counts for each pixel intensity are normalized to range 0 to 255 before they are displayed on the graph.
I used JavaScript in combination with WebAssmebly to create this tool.
How Are Greyscale Values Calculated
I'm using the following formula to convert red, green, and blue values to greyscale
luma = 0.299*red + 0.587*green + 0.114*blueUseful links
If you want to know how to generate and show image histogram on Android, you can check out my blogpost where I'm giving more technical details about this topic
I also created some other tools related to photography and image processing. If you'd like to automatically stitch multiple overlapping photos, you can check out my tool that I've created for web and for Android
https://play.google.com/store/apps/details?id=eu.sisik.panotool
You are allowed to use the generated histogram graph images and data freely for any commercial or non-commercial purposes, and you also don't need to give attribution (although linking back to my site is always nice ;D).
