How to Resize photos to specific dimensions in cm without losing resolution

Discussion in 'Mac Apps and Mac App Store' started by manimalfully, Mar 20, 2010.

  1. manimalfully macrumors newbie

    Joined:
    Dec 4, 2009
    #1
    I searched this topic in the forum and there's a few hits, but they're old and I don't really get them.

    I have a few pictures I took with my digital camera and I want to print them and put them in a frame that is 11.5cm * 7.7cm. So, I need to adjust their size to print them that size.

    I don't have a colour printer, so I'm printing off a library computer in colour, so I can't print them directly off my mac. I'm going to need to transfer them on a usb and open them in windows on a library computer. The pictures are in .JPG format since I uploaded them.

    -So I went to Preview (program) and Tools > Adjust size.
    -I typed in 7.7cm for width and it gave me a locked length of 11.1cm as that would probably keep the pictures proportionate. I'm alright with that.

    But then, when I look at my picture, it's much smaller that the actual dimensions of 7.7cm.
    Then when I zoom in, it is pixelated. That'd odd because I'm actually reducing the dimensions of my picture.

    How do I adjust their size so they print to 11.1 cm * 7.7 cm?
     
  2. deep diver macrumors 65816

    deep diver

    Joined:
    Jan 17, 2008
    Location:
    Solon, OH
    #2
    There is more to this than the dimensions. Image size and resolution are the important elements. If my image size is 300x300 pixels and the resolution is 300 pixels/inch. The size cannot change. I can reduce the resolution but I can't increase the resolution. If I want to print a 1"x1" print then My effective resolution is 300 pixels per inch. If I want a 2"x2" print then my effective resolution is 150 pixels/inch. If your image is small then you are going to be limited in how large a print will look good.

    You do not say anything about the original file format or the software you are using for the conversion. You might have to make adjustments in printer settings.

    I would suggest one of two things:

    1) Assuming the original file is large enough... Go to whatever place offers inexpensive photo printing. Most stores that sell cameras will do printing. The machines they use will do all of the resizing. If the file size is too small then the processing software will flag that.

    2) Post a message here with the original file as an attachment. I'll take a look at it.
     
  3. manimalfully thread starter macrumors newbie

    Joined:
    Dec 4, 2009
    #3
    Hey deepdiver,

    Firstly, I edited a bunch of stuff in my original post to clarify more, skim over it once more.

    I totally understand what you said about the pixels, as it's impossible to increase the resolution of an image, you can only decrease it OR leave it the same.

    The pictures are on another laptop, so I can't post 'em now. But the size of the image was 1.2MB and I'm sure the dimensions were around 861 × 1244. (I know this because I kept looking at it after adjusting the size and stuff)

    Also, I edited my original post as I said, but I'll list down a few things:

    1. I made a mistake by saying I 'converted to jpg', actually they were originally jpeg when i uploaded from the camera.

    2. I'm trying to reduce the image size, and keep the same resolution, not increase it. The problem I had was I reduced the image size from 31cm*43cm to 11.1cm*7.7cm. And when I did, the picture became much small than 11.1cm, and when I zoomed in, it was pixelated.

    3. Whenever I press print and then print preview, Preview always shows the image being printed in the dimensions of a full white paper.

    So I'm kinda confused about this.

    Thanks for the help deepdiver!
     
  4. deep diver macrumors 65816

    deep diver

    Joined:
    Jan 17, 2008
    Location:
    Solon, OH
    #4
    Hey manimalfully.

    I am starting to understand this better now. It is not clear to me from your post if you actually printed the image.

    If not, then print it. In the print dialogue box you need to choose the "scale" option in the bottom half of the window, and scale it to 100%. You could also not change the size of the image at all and just scale the original at the time of printing. Either way, it should turn out as you want.

    As for the pixilation: You are certainly correct that when you reduce the size of the image you are not changing the resolution but you are reducing the number of pixels. When you zoom in on the smaller image it gets pixilated just as it would if you over-enlarged any image.

    Let me know what happens.
     
  5. manimalfully thread starter macrumors newbie

    Joined:
    Dec 4, 2009
    #5
    Wow, very interesting stuff. You were totally right about the scale thing! When I make a picture small in preview, then it automatically increases it's scale value to make it print on the whole page. So the scale value went from 56% to 226% when I changed the image's size from really big to 10.1cm*.7.7cm. Then, I manually changed the scale to 100% and TADA, it was the size I set it to.

    But I just realized there is another problem. When I resize the image's width from 33cm to 7.7cm, it changes it. But when I click actual size, the width seems smaller than 7.7cm. So I used a ruler to see how long it is on the screen (during actual size), and it's only 5cm, not 7.7cm. Why is this happened?

    Also, I will try and print tomorrow deepriver! :)
     
  6. deep diver macrumors 65816

    deep diver

    Joined:
    Jan 17, 2008
    Location:
    Solon, OH
    #6
    It is very unlikely that your monitor is going to display the image in its true dimensions. If you do need to display the image in its true dimensions then you'll have to adjust that using the zoom options in the View drop down menu. Problem here is that Preview does not let you zoom to an exact percentage, so the best you'll do is get close. Ultimately, however, if it prints properly then it is all good.
     

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