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
Related
I am trying to crop and swap different parts of a big 800x800 image and re-create 800x800 image using imagemagick with this command.
magick mogrify titli.gif -crop 2x4# +repage -reverse -append -path converted titli.gif
my problem is "-append" creates tall image (400x1600) & "+append" creates wide image (3200x200)
How can I get a large image of original size 800x800 but with cropped and swapped (reversed) parts set in "mosaic or tiled" style...
If I understand the question, you shouldn't need "mogrify" to do that. Just "magick" should accomplish that task.
It looks like you'll have to crop the image into 8 pieces, reverse them, and "-append" them vertically as you've done.
Then after that, and in the same command, you'll need to crop that result in half vertically and "+append" those two pieces horizontally to get the 800x800 output.
This example command shows how it works...
magick in.png -crop 2x4# -reverse -append -crop 1x2# +append out.png
If you're doing any more operations within the same command you'll probably want to use "+repage" after the "+append" to reset the image geometry back to WxH+0+0.
I'm trying to crop image by height with this command line:
convert 1053257.png -gravity South -crop 2910x3312+0+0 -background black +repage image-cropped-top.png
The generated image is not cropped correctly, as the dimensions after running the command are 2791 x 3312.
The width is cropped as well!
Can anyone help with this?
The general form is:
convert input.jpg -crop WIDTHxHEIGHT+0+0 result.jpg
If you want to crop to a specific width, say 1024, leaving the height unaffected:
convert image.jpg -crop 1024x+0+0 result.jpg
If you want to crop to a specific height, say 768, leaving the width unaffected - note the height is after the x:
convert image.jpg -crop x768+0+0 result.jpg
If you want to crop to a maximum width and height, say 1024 wide by 768 tall without distorting the aspect ratio:
convert image.jpg -crop 1024x768+0+0 result.jpg
If you want to crop to a specific width and height, say 1024 wide by 768 tall and are happy to allow gross distortions:
convert image.jpg -crop 1024x768+0+0\! result.jpg
Think of the exclamation mark as meaning "just do it!". Note that the backslash is only needed on Linux/Unix/macOS to escape the exclamation mark, you omit the backslash on Windows.
Note, if you are saving the cropped image in PNG format, you probably want to reset the page afterwards so the image "forgets" it used to be part of a larger image:
convert input.jpg -crop 1024x768+0+0 +repage result.png
With ImageMagick a problem like that can occur if you've done a "-trim" to the image before the crop. When you "-trim" an image it can still remember the original page dimensions from before the trim, then when you crop it, it uses those page dimensions as the starting reference for the crop. You probably need to "+repage" before the crop to start with fresh paging information. Try something like this...
convert 1053257.png -gravity South +repage -crop 2910x3312+0+0 +repage image-cropped-top.png
i'm having a large jpg, which has a resolution of x * 256 / x * 256. I want to cut this image into 256x256 tiles with a naming convention {zoom}-{x}-{y}.jpg. In the past i've used ZoomifyExpress Converter which does the cutting and zooming. I also want 6 different zoom levels. I've started so far with this command:
convert example.jpg -crop 256x256 +gravity -set filename:tile
./tiles/%[fx:page.x/256]-%[fx:page.y/256] %[filename:tile].jpg
This produces a lot of x-y.jpg tiles.I don't know how i can add different zoomlevels. I'm relativly new to ImageMagick and this feels like a basic thing to do. Hopefully somebody can help me out. Thanks in advance.
I found the solution:
I just resize the image to the appropriate size and then crop it. The first number in the filename is the zoom level.
convert example.jpg -resize 256x256 -crop 256x256 -set filename:tile
./tiles/0-%[fx:page.x/256]-%[fx:page.y/256] %[filename:tile].jpg
convert example.jpg -resize 512x512 -crop 256x256 -set filename:tile
./tiles/1-%[fx:page.x/(256)]-%[fx:page.y/(256)] %[filename:tile].jpg
.. and so on until i reach the highest resolution.
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