I want to resize/scale an image. The originals have not the same dimensions like 300x200 or 512x600. I want to resize the image to 100x100 but DONT crop anything from the image or change ratio. Ideally the image will be first scale the long edge t开发者_C百科o 100 (aspect ratio) and then fill up the smaller edge with white.
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I dont use Paperclip or Rails, just RMagick.
I've done it with merging the resized image with a new 100x100 image. That's for sure not the best way but it works:
img = Magick::Image.read("file.png").first
target = Magick::Image.new(100, 100) do
self.background_color = 'white'
end
img.resize_to_fit!(100, 100)
target.composite(img, Magick::CenterGravity, Magick::CopyCompositeOp).write("file-small.png)
After playing with it for a while I got Fu86's composite trick to work like so:
img = Image.read("some_file").first().resize_to_fit!(width, height)
target = Image.new(width, height) do
self.background_color = 'white'
end
target.composite(img, CenterGravity, AtopCompositeOp).write("some_new_file")
AtopCompositeOp
seems to work better than CopyCompositeOp
, which turned part of my background black for some reason.
image = Magick::Image.read("filename").first
resized = image.resize_to_fit(width, height) # will maintain aspect ratio, so one of the resized dimensions may be less than the specified dimensions
resized.background_color = "#FFFFFF" # without a default, background color will vary based on the border of your original image
x = (resized.columns - width) / 2 # calculate necessary translation to center image on background
y = (resized.rows - height) / 2
resized = resized.extent(width, height, x, y) # 'extent' fills out the resized image if necessary, with the background color, to match the full requested dimensions. the x and y parameters calculated in the previous step center the image on the background.
resized.write("new_filename")
Note: on heroku, which as of this posting uses imagemagick 6.5.7-8, I needed to multiply the x and y translations by -1 (and send positive numbers). Version 6.8.0-10 expects negative numbers.
It seems you want to use change_geometry...
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