Calculate DPI of image - image

I have an image on a canvas. That image will be resized by user.After that, the canvas content will pe printed at a specific dimension.
I want to calculate the DPI of the resized image, so i can tell the user if he resized to much and the printed quality will be affected.
Does someone know a formula for this?

DPI means dots per inch.
Divide the pixel size of the image with its physical dimensions in inches.

Related

What is the image editor's resolution tool for?

I have an image that is 320 x 482 pixels size and 72 PPI. I can change the image resolution with GIMP for example, but why would I use it if the images suits its pixel size for each display pixel size? I mean, an image changes its size in inches depending on the display density, right? So why would I want to change the PPI of an image, that doesn't make sense to me, although I understand that GIMP and any other image editors wouldn't put this feature for nothing.
PS: I tried to change the resolution of some images and compare it with the original image and apparently nothing happened but the size in inch of the image.
An image's DPI is defined by the capturing hardware and will impact it's size when printed out.
Changing the resolution won't change the number of pixels in the image.

Image intensity appears higher in MATLAB

I have a 2D DICOM images that appears (as it should do) to have a high intensity center, with the outside area having an intensity that approaches zero. When I load and view in MATLAB R2021b:
img=dicomread('image.dcm');
imshow(img);
The intensity appears much higher. I worry that this has affected the actual pixel intensity values and isn't just imshow trying to increase visibility. Has anyone any ideas how to get rid of this correction?
Regular image
,
Image in MATLAB

Why do images have a ppi value?

When a file describes an image it should work somewhat like this: color value of the pixel in the upper left corner = whatever. next: the color of the second pixel = whatever. and so on. so that in the end I have a description of say 1000x1000 pixels. now how can this image description have a ppi value? if I have a screen that has 1000x1000 pixels and is 22" in size, the dpi will be different from a screen with 1000x1000 pixels and 24". so the dpi depends on the screen that I use to view the image, it's not a property of the image. but images do have a ppi value, I just don't understand the logic behind that?

Matlab GUIDE blurs image?

my plan is implementing an image in a Matlab GUIDE figure. Somehow the output is always blurred (see screenshot). On the left you can see the image in Photoshop on the right in Matlab - notice how the font and other parts become blurred.
I experimented with JPEG and PNG file formats (no compression), I also tried various pixel sizes(resolutions smaller, same and bigger as the actual position of the image) and DPI(values between 30-300) settings, because I expected some scaling issue. Somehow I am stuck - Looking forward to your input!
Thank you,
Florian
Screenshot of the issue: http://s1.bild.me/bilder/260513/6875414Screen_Shot_2014-06-29_at_23.19.34.png
Most probably the reason for the blur is interpolation.
If the axis size you allocated for the image is different from the size of the image MATLAB will resize the image to occupy the whole area.
In order to prevent any interpolation you must set the axis dimension to be the image dimension.

In Magento how can i maintain image quality when i re-size the image with lower pixel

I want to show the image as good it is in it's actual size even when i re-size it with lower image pixel.
what? If you resize the picture, the pixel-count is lowered. There is no way to resize an image without loosing quality.

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