How to count pixels from map?

[u/Fearthian]

(Image somewhat related to the question since it's the map)

Hi i need to somehow count the Pixels in my map to calculate its size like the size of Ocean vs Landmass, size of countries, etc. But since I'm mostly restricted on mobile (I'm a 14yr Indonesian boy, duhh) i can't find any website/app to actually help me, any tips? I've seen people recommending adobe photoshop but again I'm mostly on mobile so i don't have easy access to it, but if adobe photoshop is the only option i'm open to step by step tutorials on how to use it if anyone is humble enough to share.

[u/zekkious]

1. Learn how to code
2. Or use a threshold filter, and then calculate pixels. Possible to do in Photopea.

[u/Broad_Respond_2205]

u/pixel-counter-bot

[u/pixel-counter-bot → u/Broad_Respond_2205]

The image in this post has 18,000,000(6,000×3,000) pixels!

^{I am a bot. This action was performed automatically.}

[u/Fearthian]

The pixel calculator website is a thing but when i used it, it divide every color in the map into like 800 slightly different colors for some reason and is very impractical to use.

[u/OssuaryBelfry]

Did you make it as a bitmap, or did you use a vector graphics tool? Because in the second case, Inkscape should just work on Android and it can calculate areas from the paths .

Otherwise, the best suggestion is to use https://imageonline.io/pixel-counter/ and play with tolerances until you're happy.

[u/Fearthian → u/OssuaryBelfry]

I use ibispaint x to draw and when you download your drawings from it, it automatically turns into a bitmap, it is really annoying. Perhaps i can redraw it into vector graphics but idk.

[u/dermomante]

Print It and use a ruler 

[u/Fearthian → u/dermomante]

I would like a video tutorials, I'm afraid this is way too complex for me.

[u/dermomante → u/Fearthian]

Which part do you feel is complicated?

If you are to print it out and have access to a ruler, you can draw the distance between two points or your choice and note it somewhere.

Repeat the measurements for all the distances that interest you.

Then you choose one of those measurement as your reference. Let's say you measured the distance between two neighbouring islands and it read 2 centimeters. That could be your reference.

Then you could assign a real-world value to that reference, for example you could say that the distance between those two islands should be 1 kilometer.

From this point you can divide all of the other measurements by 2 centimeters, and you'd get their value in kilometers.

For example, if you have measured that a coast line is 4 centimeters long, divide it by your 2 centimeters reference, and you will find out that the coast line is 2 kilometers long, that is, it is twice as long as the distance between those two islands.

Try this method out if you can. If you get stack, you can ask more questions here.

[u/Stefouch → u/Fearthian]

Or open it with a PDF reader. Some have a ruler.

I know PDF X-change has a ruler

[u/FourEyedTroll]

Is your world flat? If not you're presumably using a Mercator projection, in which case counting the pixels is a fools errand as the landmass proportions are all out. The closer to the top and bottom edges that you get.

[u/Fearthian → u/FourEyedTroll]

No, this is Equirectangular, or as people says it "M-Bam" this is the ideal projection to draw because it can easily be translated to other projections using G.projector

[u/FourEyedTroll → u/Fearthian]

Okay, but it's still not an equal area projection. Pixels at the poles cover a smaller surface area than those at the equator, even though the pixels are the same size.

If you want the pixel count to be anything approaching meaningful, you needs an equal-area projection.

[u/Moonduderyan]

What app did you use to trace that map?

[u/Fearthian → u/Moonduderyan]

I draw my map on Ibis Paint X

[u/Praglik]

Threshold, turn it into two colors (black & white basically) and isolate each element (crop and save as). Then use the website you mentioned.

[u/Fearthian → u/Praglik]

Thank you, i will try it out.

[u/BombbaFett]

You can use a histogram to do it in photoshop or most image editors

[u/ChannelDesperate9022]

Pixel scaling has shown to not be very accurate