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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Usage questions which are too arcane for the normal user list should also be posted here. This ‘hint’ can possibly be automatically evaluated by printer drivers or by page creation programs such as LaTeX.

In any case you are creating a bigger image consisting of rows of pixels which are each pixels high x pixels. Whatever is noted as ‘Resolution’ or ‘Density’ inside an image file, is a metadata attribute. Specify the units – I seem to remember having a problem when I omitted this option although DPI should be the defaultfor example:.

According to these two pieces of info Gimp then calculates the total number of pixels it has to use extrapolate from the original number of pixels to fill the requested space at the requested resolution. PNG image data, x8-bit grayscale, non-interlaced output. JakeGould 31k 10 93 Yes it is a little archaic.

So-to-speak I “executed” your code manually.

Does -resample use a different algorithm for convrt from -scale? Now there are different algorithms which can be used to compute what color values these 4 pixels 3 of them new pixels should have:. This command does not make any different with density.

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It is just a hint which a printing or rendering device or an application may or may not follow when printing, rendering or displaying the image. If you ‘print’ it at dpi imagmeagick a 1 inch square, it’s no longer the same image: I needed to put -density before input. But this is no more than a ‘hint’ attribute that does not alter the underlying raster image.

Photoshop stores its hints about a desired print or display resolution in a proprietary profile named 8bim. Home Questions Tags Users Unanswered. IT isn’t a problem that the quality will deteriorate, because the image is needed cohvert for the process of making the document not for the document itself.

That’s the reason why you made this discovery: Also, ImageMagick does not support ‘printing’ as such. Usage questions are like “How do I use ImageMagick to create drop shadows?


ImageMagick source code and algorithms are discussed here. Sign up using Facebook. IF an image viewer understands it, it will render the image larger or smaller to meet that DPI request, but it will not change the image per se. I have explained my use-case in detail inside the question. Maybe I was talking too technical, and was not clear enough? For raster images, the DPI setting is only relevant in ikagemagick context of printing or displaying it.

How can I measure my screen? Sign up using Email and Password. ImageMagick does not touch this profile, even when asked to write a resolution change into the metadata of an image file.

I discovered that pngcrush not an ImageMagick tool can also add the density metadata. This should set the DPI toas I can read everywhere in the web.


When I change them to e. This photo that I want to convert concert for internal use of government office only. Now there are different algorithms which can be used to compute what color values these 4 pixels 3 of them new pixels should have: And ImageMagick’s documentation is in full agreement with me: And ImageMagick’s documentation is in full agreement with me:.

Attributes, Properties and Artifacts http: I am often doing that when I am working with LaTeX, or to be exact with the command pdflatex on a recent Ubuntu-Machine.

Convert to dpi – ImageMagick

This is new to me. This gives you Is it a bug? Select all convert -density???

Sumanta Pakira 2 13 Nov 28 ’16 at How can I calculate how much scaling it needs in order to be at dpi? Post Your Answer Discard By clicking “Post Your Answer”, you acknowledge that you have read our updated imagemaigck of service imagenagick, privacy policy and cookie policyand that your continued use of the website is subject to these policies.

Do you know which embedded data fields GIMP uses to read the resolution – does it have its own that override the standard ones used by ImageMagick?

If you answer questions just by title you are not a help to anyone here.