elixir-image/image

Image.replace_color seems be to lowing the DPI

Closed this issue · 3 comments

tielur commented

I noticed when using Image.replace_color the images DPI is much lower after writing it to the file system.

"original_file.jpg"
|> Image.from_binary!() 
|> Image.replace_color!(replace_with: 255) 
|> Image.write!("imaged.jpg", quality: 100)`

My original_file.jpg image is 300 DPI and when I check the DPI of imaged.jpg it's 72

kipcole9 commented

That's totally unexpected for sure. Thanks for the report. It appears the underlying libvips operation Operation.ifthenelse/4 doesn't set the x-resolution or y-resolution. I've forced them to be set in commit 16aa588.

Would you consider checking this works correctly for you by configuring image from GitHub before I publish to hex?

I'm also a big curious about:

"original_file.jpg"
|> Image.from_binary!()

I would have expected:

"original_file.jpg"
|> Image.open!()

But perhaps this is just example proto-code?

tielur commented

That's totally unexpected for sure. Thanks for the report. It appears the underlying libvips operation Operation.ifthenelse/4 doesn't set the x-resolution or y-resolution. I've forced them to be set in commit 16aa588.

Would you consider checking this works correctly for you by configuring image from GitHub before I publish to hex?

Just tested it with the master branch on github, it works!

Thanks for the quick reply and fix!

I'm also a big curious about:

"original_file.jpg"
|> Image.from_binary!()

I would have expected:

"original_file.jpg"
|> Image.open!()

But perhaps this is just example proto-code?

Yeah I was loading the file via File.read!/1 prior, so just bad pseudo code example

Thanks again!

kipcole9 commented

Yeah I was loading the file via File.read!/1 prior

I recommend Image.open/ primarily because libvips streams image data on demand. Effectively it builds an operation pipeline until you call Image.write1/2 (or other functions that materialise the pipeline).

Therefore Image.open/2 doesn't read the whole image into memory (unlike File.read!) - it only streams image data as it needs it.

I'll publish the new version of image now.

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