c# Image size increases after saving it

Question

I'm trying to save the image as follows:

var file = Image.FromFile(@"D:\front.png");
file.Save(@"D:\front_save.png");

Size of the saved imeage increases almost twice the size of original one. How do I save the image so it's completely the same as original image?

Image Link

Does Saving it as such `file.save(@"Image\Path", ImageFormat.Png)` Make a difference? — Tom, Aug 29 '18 at 10:20
i think this is because the Image class reencoded the image. — Noren, Aug 29 '18 at 10:26
@EugeneBelov I Can't seem to replicate this error with a 8kb png it outputs the same 8kb file — Tom, Aug 29 '18 at 10:27
Possible duplicate of [How to copy a file to another path?](https://stackoverflow.com/questions/1979920/how-to-copy-a-file-to-another-path) — mjwills, Aug 29 '18 at 10:41
What size is increasing? The space it takes on disk? From what to what? The size it has when displayed? Is the code real? — TaW, Aug 29 '18 at 10:50
Maybe the original has a reduced color set? This can take the image down from 29 to 9 mb — TaW, Aug 29 '18 at 10:56

score 0 · Answer 1 · answered Aug 29 '18 at 11:54

Unfortunately, .NET doesn't expose any way to control the parameters that are applied as part of the PNG compression. Since PNG is a lossless format, the two images are "the same", they're just stored differently. What ever tool saved the original image must use different compression parameters than the default .NET PNG compression defaults, resulting in an optimized file size. When you save from .NET, the default compression parameters result in a larger, non-optimized, file size.

The answer to this question lists some third party libraries that you could use for PNG optimization. If you're not concerned about losing information, you could save the image as a jpeg.

I don't have enough rep to comment in the original question. But I just realized that @mjwills solution of using File.Copy() would do exactly what you want as long as you don't need access to the Image in C#. — Sterling C., Aug 29 '18 at 12:19

c# Image size increases after saving it

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