Specify the units – I seem to remember having a problem when I omitted this option (although DPI should be the default), for example: convert. convert -units PixelsPerInch -size x xc:black -resample 96 The GIF format actually totally ignores/discards the dpi anyway, as you can see diff finds. #resample. As for your screen — measure it! it is typically (these days) 90 to dpi. Remember dpi.

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What are you even talking about. But this is no more than a ‘hint’ attribute that does not alter the underlying raster image.


Funny enough, the same output comes for input. In other words it is more than likely that the two aspects are causing buggy behaviour. I figured out how to get. I needed to put -density before input.

Why does ImageMagick always convert to 96 dpi? Keep doing what you want to do with Gimp when you print. In any case you are creating a bigger image consisting of rows of pixels which are each pixels high x pixels. That is the first info.

So what remains is this: So-to-speak I “executed” your code manually. Whatever is noted as ‘Resolution’ or ‘Density’ inside an image file, is a metadata attribute.

Am I getting something completely wrong? But a different order is recommended with current IM versions so that it works for all images: Usage questions which are too arcane for the normal user list should also be posted here.

Exiftool also is able to set parameters, but as noted in man page Image:: That is a global setting that is saved so that cknvert images can use the value when they are ‘rasterized’.


The question clearly asked how to change this field without changing the pixel data. One example, where the resolution value noted by ImageMagick inside the image metadata is NOT honored by an application is Adobe Photoshop.

Thanks Mark, sorry that I did not mention that, I want to just change the DPI of the image, the same command is working in Windows but its not working on Linux. Yes it is a little archaic. Imagemagik also happens imagemwgick be a field that can be stored in an image file for when this resolution is relevant.

And ImageMagick’s documentation is in full agreement with me:.

The program as shown uses constants for little-endian machines, like x I am also open to other automated solutions which are easily done on a Linux system. Post Your Answer Discard 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. For raster images, the DPI setting is only relevant in the context of printing or displaying it.

Sign up using Facebook. Sign up or log in Imagemaglck up using Google. Photoshop stores its hints about a desired print or display resolution in a proprietary profile named 8bim.

convert image 75 dpi to dpi – ImageMagick

I don’t know whether ImageMagick has resolution-changing options, but would be surprised if it doesn’t. I am often doing that when I am working with LaTeX, or to be exact with the command pdflatex on a recent Ubuntu-Machine. Ok, the values there are often 72 by default. Did you even understand what I tried to say in my comment?! I would probably have expected something similar with units, in which case order between the two should not matter.


I’m going to guess that these are for passport photos of some sort? Some other image formats JPEG? Is it a bug? Now what is the problem here. Home Questions Tags Users Unanswered. Post Your Answer Discard 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. This is new to me. It may look nicer to the human eye convedt your scale up algorithm is a ‘good’ one.

If you’re concerned about both reliability and speed, then I recommend ignoring that statement about DPI and just experimenting. Note that you can use Exiftool to read out resolutions. Then you show how the image i,agemagick after the command and it shows 12dpi. A higher DPI will transfer convet picture information into the raster format and hence preserve more details from the real original quality.

However, scaling up a raster rpi by making it contain more pixels does not add real info to it, and it does only add ‘quality’ to it which is fictitious. It doesn’t make sense with ImageMagick. Select all convert -units PixelsPerInch rose1.

Nov 28 ’16 at With that use normal convert resize: