I want to submit some images to IEEE journals. there stand is image should be in at least 300dpi. I originally created my image using screenshot. its original size was 392*143 (pxels) and resolution was 96*96 (dpi).
then i used GiMP and go Image > scale image > X and Y resolution to (300)
then i export it.
yes, in the property of the image it shows now resolution as 300*300 dpi.
when i open the image, I can not see that it has high resolution quality that my original. because still to the computer screen my original image look good.
Did I do something wrong? should I change the size when changing the resolution, but i feel if i give a larger size than original size then the new image might verse.
can anyone tell me, how can i get a quality high resolution image (at least 300 dpi) using low quality image. thanks
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I was just going over the book HTML&CSS design and build websites by Jon Duckett, I'm currently on the Measuring Images and Resolution section, and had a question on the part that says
"On a screen, an image is that is 300x300pixels at 72ppi looks exactly the same as an image that is 300x300 pixels at 500ppi."
Why is this? (let's say for this case, the screen resolution is same for both 1680x1050px) I've been trying to figure out why, but having trouble understanding why it would look the same. There must be something that's working to make it look the same right?
For example,
what happens when you set an image with a fixed size of 300x300px, but the image ppi is greater than screen ppi, or when an image ppi is less than a screen ppi? Does the image somehow get reduced/added pixels?
Hope my question makes sense!
If screen size is 13"x8.125" resolution is 1680x1050px then the ppi for the screen is about 129ppi.
and if the 300x300px image is 72 ppi, then 72 is much less than 129, what fills these 57pixels that the image does not provide?
And for the 500ppi image, it would be too much?
I have a photo with a size and pixel diemensions as shown below:
I opened and saved it using Matlab, and the size of this photo becomes much smaller, and also a smaller dpi value. But the diemension is still the same.
Then I converted the two to .bmp format, and the bmp images are in the same size! Does the dpi value correlate to image size, or there are other reasons behind?
When an image is described as 7952× 5304 pixels, then the dpi value is of no consequence. It means nothing.
Where the dpi value comes in, is in describing how large the image will be printed.
You can always resize the image to the dimensions you want with imresize.
I am trying to understand the relation between image pixels, their size, resolution and how changing the resolutions of an image results in the same image size but slight amount of blurriness. I referred to this links but some doubts still remain:
1) So, what is the "commonly" accepted definition of "resolution"?
2) How(and Why) does changing the resolution of an image (say, a Desktop wallpaper) result in the same image size but a slight amount of blurriness? In this case, what definition of "resolution", "pixels" and "image size" are we talking about?
Thanks in advance!
The image that is displayed on the screen is composed of thousands (or millions) of small dots; these are called pixels.
The number of pixels that can be displayed on the screen is referred to as the resolution of the image.
Image resolution is the detail an image holds.
As the resolution goes up, the image becomes more clear. It becomes
sharper, more defined, and more detailed as well.
In addition to image size, the quality of the image can also be manipulated. Here we use the word "compression". An uncompressed image is saved in a file format that doesn't compress the pixels in the image at all. Formats such as BMP or TIF files do not compress the image.
If you want to reduce the "file size" (number of megabytes required to save the image), you can choose to store your image as a JPG file and choose the amount of compression you want before saving the image.
These terms are explained in a video
Put in simple words, resolution is simply the number of pixels(picture cells) contained in a horizontal/vertical axis. The more the pixels arranged in an axis, better the image. The formal definition can be easily availed on the web.
Changing the resolution simply means changing the number of pixels in the image.Higher resolution implies more pixels hence a more detailed image. Reducing the resolution of an image decreases the image size following either lossy or lossless compression algorithms. This further reduces the amount of information in the image leading to the blurriness or the jagged edges.Image size varies according to the degree of compression only. 'Pixels' and 'Resolution' remain what they had been explained.
I'm making a website with a single image as a background (with different backgrounds for subpages). So far I have established that the image should be about 1920x1080, possibly with 1.77:1 aspect ratio and a jpg for PCs. Now I want to reduce the image file size without losing quality.
1) First my problem. I have encountered the most bizarre thing in photoshop. When I upload an image 4272x2848 that weights 521 KB into photoshop and save it without changing anything, its size increases to... 1,52 MB ??? After I cut down the size to ~1920x1080 the size is still ~800 KB. Also the image before uploading has 96 DPI, after it is uploaded it changes to 72 DPI. (What sorcery is this?)
2) What is an acceptable image file size with that resolution?
3) Should I use save for web? This increases the size or reduces the quality from what I have experimented.
4) I found this image size reducer website: https://kraken.io/web-interface It reduces the size and I think the image quality does not change.
5) http://www.filedropper.com/pancakes - the image from question #1. (The image will probably be changed in the near future so this one is more of a case study).
Thanks!
JPEG being lossy, every time you load, then save, a separate JPEG algorithm is applied again. I believe the default for Photoshop is High quality, which an 8 on their dialog. So if you have an original JPEG that was originally saved as a low or medium quality (say a 4-6 on the Photoshop dialog), if you then open that in Photoshop, and go with the default "High/8" quality save, then the JPEG algorithm is applied on the perceptual image, meaning you saved a lower quality perceptual image at a higher quality algorithm's amount of data.
This is a major reason that I've moved away from JPEG. If JPEG is required I always try to start with either a RAW, BMP, TIFF, or PNG image, and then save off a JPEG version from that, then if I need to make any changes I go back to the full "original" [lossless] format, make the changes then save the JPEG again. I try to never edit an image that is already saved as JPEG, because you're always going to lose a small amount of quality (mostly the JPEG algorithm is good enough that the loss of quality isn't perceptual, but the file size can change none-the-less).
Just wondering:
I'm trying to set up an adaptive image handler in Coldfusion8, which resizes images for smaller screensizes.
I have it working allright and am currently playing around with the different resize options found here
What I notice is no matter what method I'm using, they all take time, reduce the image quality and not really reduce the image size, so for example:
IMG 1 IMG 2
Original 23K 900x360px 53K 900x360px
Blackman 22k 320x128px 52K 320x128px
highPerformance 21K 320x128px 32K 320x128px
nearest 25K " 38K "
The idea was to resize images for smaller displays. Right now I'm not really reducing anything, I'm only drainging the processor for resizing and output blurry images and the same file size.
Question:
Why should I bother resizing then? I might as well send the original file which #900x360px #23K. At least that images will be sharp vs. a resized blurry image with 320x1280px. Is there a way to make resizing images in Coldfusion worthwhile in terms of file size and/or image quality?
Thanks for inputs!Cldfu
I think what you fiddle with are quality/speed of the resize algorithm, not compression.
To compress with better file size, set the JPEG compression quality using the quality attribute (default to 0.75)
http://help.adobe.com/en_US/ColdFusion/9.0/CFMLRef/WSc3ff6d0ea77859461172e0811cbec22c24-7945.html
If cfimage doesn't satisfy your needs, use imagemagick