I'm trying to determine the Pixel Aspect Ratio (PAR) of a given image and am trying to use Imagemagick:
magick.exe c:\tmp\foo.0001.tif -format "%[fx:w/h]\n" info:
This gives me the aspect ratio of the image, though not the Pixel Aspect Ratio. From some digging, it looks like ImageMagick may not be able to do this, but I don't have a definitive answer. Is this possible? Or is there another tool I can use?
In ImageMagick, this should do what you want:
magick input.tif -format "%[fx:resolution.x/resolution.y]" info:
Related
I need to resize an image and the result image should have 300 pixels in height. The image must keep the aspect ratio of the original image.
To specify the height and keep the aspect ratio, use -resize x300
magick convert -resize x300 in.jpg out.jpg
For Windows users:
"C:\Program Files\ImageMagick-7.0.8-Q16\magick.exe" convert -resize x300 in.jpg out.jpg
(change the "7.0.8-Q16" with your own version of ImageMagick)
For more ways to specify the target size, see https://imagemagick.org/script/command-line-processing.php#geometry
I have images of unknown size and ratios. I wish to take a centred 16:9 crop.
If all the images were known 4:3, then it's easy: 9/16 รท 3/4 = 0.75 so I simply set the height to 75% of the original like this:
convert photo.jpg -gravity center -crop '100%x75%' +repage photo16x9.jpg
However, if the photo is already 16:9 (or even wider), I don't want to crop it, and if it is 'taller' than 16:9 I want to crop it only by the amount necessary to achieve a 16:9 crop.
This would be also easier if I wanted to scale to a known width or height (example question for that). But I'm looking to leave as much of the original image data in place as poss.
Therefore I'm looking for a way to crop the height to a factor of the image's width, with a cut-off.
I hoped this might work
convert photo.jpg -gravity center \
-crop '100%x[fx:9/16*w]' +repage photo16x9.jpg
but alas it seems the [fx:...] is not allowed in a -crop argument.
Hacking a bit I found somewhere that I could not for the life of me understand(!) also failed, but I'll list it here to show research effort!
convert photo.jpg -set option:distort:viewport \
'[fx: w]x[fx: w*9/16 ]+0+0' -filter point \
-distort SRT 0 +repage photo16x9.jpg
(I realise that neither attempts above cover the case when the image is already wider than 16:9, but if the [fx:...] thing worked I could achieve that by using the ternary operator, so I kept the examples simple.)
Maybe you can just calculate the aspect ratio and use that to make a decision. Create two test images, one 15x9 and one 17x9:
convert -size 15x9 xc:black 15x9.png
convert -size 17x9 xc:black 17x9.png
Now ask ImageMagick to tell you if the aspect ratio is wider than 16:9 or less than or equal to 16:9:
convert 15x9.png -format "%[fx:(w/h)>16/9]" info:
0
convert 17x9.png -format "%[fx:(w/h)>16/9]" info:
1
I've read the ImageMagick documentation here and here and been unable to achieve a couple of simple tasks. Would appreciate any simple pointers or direction, or even commands I can execute that will work on Linux.
I want to convert any image-type (JPG, GIF, PNG, TIFF) to save to a PNG, losslessly, and as compressed as possible without any loss of quality. Ideally in 96 DPI so they look good in Retina screens.
To then take the above generated PNG and also resize it in specific sizes, with height and width specified.
What am I missing with the convert command?
If you want to convert a TIF, GIF or JPEG to PNG, the command is:
convert image.tif result.png
or
convert image.jpg result.png
In answer to your questions...
Question 1
PNG is lossless by definition, so that is not an issue. To get better compression of a PNG, you generally need to reduce the colours, i.e.
convert image.jpg -colors 64 result.png # or try 255 which allows a palettised image
The dpi is pretty irrelevant until you print on paper. More pixels are needed if you want more quality on screen.
Question 2
If you want to resize an image without destroying its aspect ratio, use
convert image.jpg -resize 200x100 result.png # retain aspect ratio
If you don't care if that makes the image look stretched or distorted, and you want exactly 200x100, tell ImageMagick that you really mean it by shouting:
convert image.jpg -resize 200x100! result.png # ignore aspect ratio
I'm given an image of unknown size. I want to shrink it such that it will fit in either 640x480 or 480x640, preserving aspect ratio. I want the image to shrink the minimum amount (e.g. the result should be the maximum size which fits in either 640x480 or 480x640).
For example, if I have a 800x800 image, it should shrink to 480x480. If I have a 500x1000 image, it should shrink to 320x640. Similarly, 1000x500 should become 640x320.
Can I do this in ImageMagick in one command? No cropping should occur, and the aspect ratio of the original image should be preserved. Thanks!
It's easy to resize an image without cropping and preserving the aspect ratio, but I don't think that you'll be able to achieve your either/or in a single command.
From the geometry specification docs, resizing an overlarge image to 640x480 is easy:
convert input.png -resize 640x480> output.png
That will only resize if necessary, won't crop, and will preserve the aspect ratio.
Depending on your input images, you might be able to use the area operator:
convert input.png -resize $((640*480))# output.png
But that will only work if all the input images already have either a 4/3 or 3/4 aspect ratio.
I think your best bet is a short shell script:
wider_than_tall=`identify -format %w/%h input.png`
if (( $wider_than_tall )); then
convert input.png -resize 640x480> output.png
else
convert input.png -resize 480x640> output.png
fi
Using Imagemagick, I'd like to convert a batch of PNGs to a fixed height of 1080px and a proportional width. With proportional I mean this: If the original Image is scaled down 16.8% to 1080px, the width also needs to be scaled down by 16.8%.
Any way of using convert without having to calculate the exact geometry before (using identify and some bash calculation shenanigans) ?
Try this:
convert -resize x1080 {from_path} {to_path}
Image geometry is an option described to use with -resize
xheight Height given, width automagically selected to preserve aspect ratio.
So you only have to specify the height
There is one additional example. give it some values to the resize parameters and it'll automatically resize your image. Plus you can chose other parameters (gravity center or crop etc.).
convert image_example: \
-resize x160 -resize '160x<' -resize 50% \
-gravity center -crop 80x80+0+0 +repage image_example.jpg
Cheers