Hello, I have a script that runs convert from the command line to resample a large number of images to 72 dpi to make them more web friendly. -resize x+20+30 (like the -scale and -sample examples below) converts an input to an output image which has the pixel dimensions of x A protip by asbigger about resize, bash, image-magick, magick, and size-in- pixels.

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As of IM v6. Thanks, that makes so much more sense than the ImageMagick documentation. That is, the image is resized to imzgemagick fill and even overflow the pixel area given. Resizing Images Ignore Aspect Ratio ‘! That is not to say you can’t use it for diagrams, or line drawings, though for that type of image you may need to use some of the more advanced options we’ll look at later.

When minifying because the input image size may be larger than xpixels are sub-sampled with a very simple algorithm: Using color correction on a low-quality Q8 version rewample IM see Quality is not recommended due to the loss of precision such a ressmple memory imagmagick provides.

Problems with resampling to change resolution Questions and postings pertaining to the usage of ImageMagick regardless of the interface. The purpose of this operator is to preserve the rendered size of an image: Thus the final resolution of the image in combination with the number of pixels will produce the resolution density that in combination matches the density needed for that hardware.

When minifying, it changes the image size simply by replacing pixel colors by averaging the respective input pixel colors together.

By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service. Each illustration shows a different result, depending on the ‘fine details’ of the exact resize method: ImageMagick uses the quality level of the input image, if possible. By clicking “Post Your Answer”, you acknowledge that you have read our updated terms of serviceprivacy policy and imabemagick policyand that your continued use of the ikagemagick is subject to these policies.


The following command asks ImageMagick imagekagick resize an image to pixels in width and pixels in height:. This is only a problem with non-linear colorspaces with mixed color-intensity channels, such as sRGB, or a sigmoidal colorspace. For a list of supported filters, simply run convert -list filter.

Problems with resampling to change resolution – ImageMagick

Can you elaborate on the difference between sample and resample? You can also specify a specific width or height and ImageMagick will resize the image to that width or height while preserving the aspect ratio.

Smarthome Office Security Linux. This is just the start of what you can do with ImageMagick. The convert command can also quickly resize an image. If you had sample images, this would be even more perfect: You can take advantage of Bash to quickly do batch processing of many images. My very limited understanding is that -resample changes the dpi. Stack Overflow works best with JavaScript enabled. All these ‘flag’ options ‘!

Not very useful and rarely used. This not only resizes the image, but strips any and all profile and comment information that may be present in the original JPEG image.

By clicking “Post Your Answer”, you acknowledge that you have read our updated terms of serviceprivacy policy and cookie policyand that your continued use of the website is subject to these policies. Additionally, there are a few more differences to -scale:. Resizing Images The most obvious and common way to change the size of an image is to resize or scale an image. So you might try: This was researched and finally fixed from that version onward.


ImageMagick is a suite of command-line utilities for modifying and working with images. IM has always tried to provide options to give you the maximum scope of control in image resizing. The Best Tech Newsletter Anywhere. Select all convert -density oldfile. The geometry argument to -sample doesn’t support any offset part unlike -resizewhich respects offset directives for the output.

If you think about it for a minute, this makes complete sense, because the perceptual colour spaces pack lots of bits at the darker end of the intensity spectrum, and “hollow out” the lighter end, so as to mimick the HVS Human Visual System.


The content of the image is then enlarged or more ressample shrunk to fit the desired size. You can easily modify this command to perform other actions. See Windows Batch Scripting for this and other windowing particularities. First of all, thank you for the highly informative answer. ImageMagick can quickly rotate an image. I am creating thumbnails from much larger images and have been imagemagici this command successfully for some time: Of course for most people, the normal default options is good enough as they were designed with general use in mind.

It does NOT fill, the requested box size. If I need to make various size large picture thumbnail with fixed aspect ratio rseample needed — what’s my best choice?

The following command takes an image named howtogeek.