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strange image dimensions

 
 Hello! Anyone good in photo editing around? I'm having a question about why a tiny white rectangle image opened in drawing app says it has in fact 17 cm? Trying to edit a flyer and when I got it printed it looks huge while on my screen it's just 12 centimeters without zooming out or other editing tools active. Here's a picture with the image properties where says it has 17 cm 🤯🤯..It's a screen resolution thing? In my case 1920×1080  (4k if I'm not mistaken) and a 16 inch display. What am I missing?



Re: strange image dimensions

Reply #1 –
Quote from: Surf3r – on
Hello! Anyone good in photo editing around? I'm having a question about why a tiny white rectangle image opened in drawing app says it has in fact 17 cm? Trying to edit a flyer and when I got it printed it looks huge while on my screen it's just 12 centimeters without zooming out or other editing tools active. Here's a picture with the image properties where says it has 17 cm 🤯🤯..It's a screen resolution thing? In my case 1920×1080  (4k if I'm not mistaken) and a 16 inch display. What am I missing?
What exactly are you trying to do in here? I think you should change the unit to pixels and then check the resolution of the image.

Re: strange image dimensions

Reply #2 –

 I want to have the printed version same size as the one I'm having on the screen. Changing the unit to pixel doesn't change the real size of the image. The question is where those 17.5 cm are while on my screen I'm having only 12 cm?

Re: strange image dimensions

Reply #3 –
Most (all?) image viewers show 1 image pixel per 1 screen pixel when zoomed "100%". But the image also often has resolution information in the metadata, for instance "300 dpi" (dots per inch), mainly for printing considerations. A computer screen has a certain resolution, too (how many pixels per physical inch on screen). It's probably not the same as the image's resolution.

Also, the resolution info in the metadata can really be anything. If you create a new image in, say, gimp, you can arbitrarily define the resolution and pixel size separately. It's just metadata. The real data are the pixels.

Re: strange image dimensions

Reply #4 –

 If it has 665 pixels long why it doesn't show it as is? 665 pixels really means about 17.5 cm wide. Can't apps figure out quickly enough so we really can have the real size of an image?

There's an online conversion tool I use so indeed 665 means 17.5 cm wide. Still don't get it why it's not shown the real size on the screen since it looks like an easy task to convert pixels to cm and vice versa so we can know how to quickly scale our images.

So on my screen looks like the small rectangle while the real size according to image properties it's as big as the larger rectangle you see there.






Re: strange image dimensions

Reply #5 –
That tool just converts lengths. "Pixel" can apparently also mean a certain obscure unit of length. In other words, that converter assumes a resolution of roughly 100dpi.

665 pixels means 665 pixels. In centimetres it can mean anything depending on the resolution used. All screens obviously don't show the same image the same size!

If you know that your printer prints, say 300dpi, scale your image to come out the right size at that resolution. For example: 300 dpi is 118.11 pixels/cm, so if you want 12cm, it needs to be 1417 pixels at that resolution. You can maybe also tell your printer to print at a given resolution, but the results might not be what you want depending on the printer.

"The real size" in some units of length makes no sense without defining the resolution. And like I said, the resolution in the image metadata is arbitrary.

Re: strange image dimensions

Reply #6 –

 I got it but one question is still up.. why apps or image formats aren't made to take into consideration any resolution, so if I'm seeing it as a 7 by 3 cm rectangle to store that metadata into the picture and when I use a totally different device that device to query metadata and the exact same rectangle to be shown.

So if I'm on a low resolution let's say 360p screen and draw a rectangle save the image and then when I open that image on a high resolution screen that rectangle should have same size as on the low resolution device. When I say size I don't mean pixels but size in sq cm or sq mm. I don't care how many pixels  a rectangle has, the most important aspect is its intended size.

Pixels will change permanently so when I will draw into the future in double UHD a tiny square that square when opened on an old device should not look like a bed-sheet.

Re: strange image dimensions

Reply #7 –
Quote from: Surf3r – on
I got it but one question is still up.. why apps or image formats aren't made to take into consideration any resolution, so if I'm seeing it as a 7 by 3 cm rectangle to store that metadata into the picture and when I use a totally different device that device to query metadata and the exact same rectangle to be shown.

 ::)
"Wer alles kann, macht nichts richtig"

Artix USE="runit openrc slim openbox lxde gtk2 qt4 qt5 qt6 conky
-gtk3 -gtk4 -adwaita{cursors,themes,icons} -gnome3 -kde -plasma -wayland "

Re: strange image dimensions

Reply #8 –

 @lq ok good, now try to make an exact rectangle of 8 × 4.5 cm (80 × 45 mm) in 300 ppi..good luck

what I'm having on the screen it should be the real size in cm by default. Too much needless theories just to draw a dumb rectangle. What we see must always be what we get. Humans don't work in ppi we work in cm so why the hell isn't that the default?

https://tube.dembased.xyz/w/km4h5iNR3qkhoo7mabfjVi

Re: strange image dimensions

Reply #9 –
Quote from: Surf3r – on
@lq ok good, now try to make an exact rectangle of 8 × 4.5 cm (80 × 45 mm) in 300 ppi..good luck

 ;)
"Wer alles kann, macht nichts richtig"

Artix USE="runit openrc slim openbox lxde gtk2 qt4 qt5 qt6 conky
-gtk3 -gtk4 -adwaita{cursors,themes,icons} -gnome3 -kde -plasma -wayland "

Re: strange image dimensions

Reply #10 –
Quote from: Surf3r – on

 If it has 665 pixels long why it doesn't show it as is? 665 pixels really means about 17.5 cm wide. Can't apps figure out quickly enough so we really can have the real size of an image?

There's an online conversion tool I use so indeed 665 means 17.5 cm wide. Still don't get it why it's not shown the real size on the screen since it looks like an easy task to convert pixels to cm and vice versa so we can know how to quickly scale our images.

So on my screen looks like the small rectangle while the real size according to image properties it's as big as the larger rectangle you see there.







Instead of that unit converter which has no option for user to enter the PPI, use this one which converts values based on your entered PPI - https://cssunitconverter.com/pixels-to-cm