Change the dpi / ppi of an image with Gimp

Published by TheJoe on

Estimated reading time: 2 minutes


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I often find myself having to create images that serve as separator content within prints, or some simple graphic effects created with tracked, or with letters. I'm thinking of something very simple, that surely even in the old schoolbooks we were used to seeing without realizing.

Occasionally, however,, I happen to create the new image, save, and realize that the work is finished the dpi is too low Gimp because those who apply by default are 72, excellent to the web but too little for a detailed Print quality. Today we see how increase the dpi of an image we have already saved with Gimp 72 dpi, and the portarla 300 (great for Print).

Read more…

the wikipedia
To “dpi” means “Dots per inch” (Dots Per Inch). It is the amount of image information that can be rendered by an output device such as a graphic printer, a plotter, a RIP or one screen. With the DPI is expressed quantity of printed dots or displayed on a line an inch long (about 2,54 cm). Generally a higher value corresponds to a higher resolution and a better yield on sloping lines.

Start now by saying that of course the final image will smaller than the original. Much smaller than the larger the detail. It is an inverse proportion : “72” (the initial dpi) Next a “300” (s final dpi) come “x” (the measures that we will get) Next a “15cm” (the initial measures).

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Let's say we have an image of 17cm of height 72dpi the proportion used will be 72 : 300 = x : 17. And the result will be 4,08cm, about a quarter of the initial value.

To change the resolution the image is enough to go on “Picture” – “Scale Image” and change the values ​​of “Resolution x” and “Y resolution“.


It is also possible Gimp configuration saved because automatically images 300dpi. In the menu “Edit” – “Preferences” under the tab “Default Image” basterà passare da 72dpi the quality that we prefer.



I keep this blog as a hobby by 2009. I am passionate about graphic, technology, software Open Source. Among my articles will be easy to find music, and some personal thoughts, but I prefer the direct line of the blog mainly to technology. For more information contact me.


Oscar · 26 October 2018 at 4:49 PM

But instead if I want to increase the resolution maintaining the size of the photo?

    TheJoe · 26 October 2018 at 5:08 PM

    What I ask does not make sense. Increasing the resolution narrows the picture because they are “condensates” a greater number of pixels in the same space, conversely increasing the size of the photo pixels will occupy a larger surface area, and then the final image will tend to blur.
    It happens only in CIS that has a photo postage stamp size are able to trace the license plate of the car killer.

      Oscar · 26 October 2018 at 5:31 PM

      As there is no point my request? If you download a photo from a Web 72 pixels with dimensions 8×5 cm impaginandola and I want to publish it keeping the format or the original size, I will have a very poor quality, increasing the resolution as I read this blog you increase the resolution to 300 but at the expense of the size which is reduced to 2,5 cm x 1,5 cm, and then I have to use the lens to look at. mistake? Thanks

      TheJoe · 26 October 2018 at 6:03 PM

      Increasing the resolution and simultaneously increase the size is impossible. So I wrote to you that your application does not make sense. The procedure you followed to increase the resolution of 300dpi is correct and the final image (as already said) It is smaller force than the original.
      But the answer to your question was already present in the article: “Start right away by saying that of course the final image will be smaller than the original. Much smaller than the larger the detail. It is an inverse proportion : “72” (the initial dpi) it's up to "300" (s final dpi) come “x” (the measures that we will get) sta a “15cm” (the initial measures).”

      I suggest using a picture suitable for printing, ie with an already good resolution departing, or – depending on what you want to create – a complementary graphics to photography or a photo collage. There may be different solutions to your problem, but for sure you can not ask a computer “invent” the pixels where there are no.

      Oscar · 26 October 2018 at 5:58 PM

      Regarding “It happens only in CIS…” I beg you to view this PDF section CDC4X .

      Obviously they are very expensive programs for the chosen few , type editorials , photographic studies of a certain level etc..

      Greetings and thanks.

      TheJoe · 26 October 2018 at 6:08 PM

      I already knew the product to show me, The technique is called interpolation and broadly will also speak in my article. Use the same technique (perhaps different algorithms, but the technique is that for years) Google also to better define the low-resolution satellite photos.
      There are several algorithms and certainly some are covered by copyright such as the one you quote. Anyhow (looks best photos of pdf that you linked me) do not allow you to enlarge an image 2,5 x 1,5 cm to be able to print.

Marina Rossi · 4 July 2018 at 5:58 PM

With simple without losing time with chatter

    TheJoe · 7 July 2018 at 5:38 PM

    Thanks for the comment, Marina. Back tuned for new items!

Sensient · 29 October 2016 at 12:43 AM

Thanks. Gimp without studying it, It makes you crazy.

Luca · 15 September 2012 at 6:31 PM

excellent article, was just what I was looking for

TheJoe · 31 March 2012 at 10:27 AM

I do not understand, however, the question of “scale image”.

In fact immediately re-adapts. If you change the value “X Resolution” (di default è linkato a “Y Resolution”) automatically changes “Width” and “Height” the “Image Size”. I do not understand your concerns.

TheJoe · 31 March 2012 at 10:10 AM

Hello and thanks for the comment Giulio.
We come to us. The Canon 5D is a full frame, this means that it has a larger sensor (with more pixels) compared to the lower-end SLR sensors. The maximum resolution of the 5D (leggo Su wikipedia) is 5.616 x 3.744.

Apriamo Gimp, we create a new image and insert the two dimensions. We select “Advanced Options” and change the dpi in 300.

It opens a white image, with the pixel dimensions. To the lower base of the sheet will find the scale factor (in my case 18,2%) and a drop down menu where you can choose between pixels, inches, mm, etc.. We choose “inches” and we place the mouse in the lower right.

The coordinates that will appear next to the drop-down menu will “47,55 x 31,70” inches. This is the maximum resolution to 300dpi which can give you a Canon 5D.

Interpolate is not demonic, but it must be used wisely. Everything depends on the work you want to achieve. If you want to print the photo on a billboard of several meters is better to create a vector image of the original. If you need to make 50 posters×70 can interpolate, but I advise you not to interpolate, and complementary to the study you a graphic picture. There are several methods to interpolate, there is also a tool inside the core of the Gimp, but the best result you reach it with a plugin which I'll discuss in the next tutorial.

In short, everything is possible, but it depends on what you are looking.

    Roberto · 25 October 2017 at 10:01 AM

    Hello, I would help, I should send for printing calendars, but ask me an image format that I just can not coincide, I could help?
    they want 330×195 mm per 300 dpi with gimp how the hell do?

      TheJoe · 25 October 2017 at 10:24 AM

      Ciao Roberto,
      It is not complicated.

      Once you click on Open Gimp “file” – “fresh” to create a new image.

      In fields “width” and “height” You will insert the size (you need to select the “mm” instead “px” from the menu).

      In the resolution range just below you will enter 300,00.

      If you have any other questions write well! And thanks for the comment!

giulio · 27 March 2012 at 1:40 PM

very clear and well done.

But I ask you a question?

I have a canon 5d by 12 megapixel, and I want to print a 50 x 70!
I bought a full-frame because before I had printed 50×70 with a sony 230 (with pasc) and the result was disgusting!

I wanted to ask if interpolated with gimp can be useful for a large print!
and how the hell do you?=) I'm using it but when I get the window “scale image” with the data within in confusion,I followed your advice but when I put 300 dpi should also readjust the measures ?precisely because it goes from 72dpi to 300?I do not understand the passage!
and then if I have to change the print size?

hello and thanks joe!

gabriele · 13 February 2012 at 7:08 PM

Clear, thanks

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