'Adjust size' option showing reduced 'resulting size' but not working

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Hi,

I am using a MacBook Air, High Sierra, Version 10.13.4. (I am fairly new to MACs)

I want to resize a jpg photo image for web use. It is currently 855 KB. If I open it in 'Preview' and select 'Adjust Size' from the Tools menu a dialog box pops up. It lists the dimensions of my image (914 x 609) and the resolution as 72 but underneath it says 'Resulting Size' - 100 percent, 194 KB (was 855 KB).

If I click 'OK' it marks the image as 'edited' even though I haven't done anything. If I save the image I see the KB size hasn't changed (still 855). I think 194 KB is probably about right for this image. What am I missing?

Thanks and sorry for the newbie question.
Gavin
 

IWT


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A warm welcome to Mac-Forums, Gavin.

You're not doing anything wrong as much as not doing anything at all:)

Open your photo in Preview as before and click on Adjust Size.

Here is what I get with a photo:

S1.png

You can see that it is a big file. Note the width is 4032. By experimenting with substituting different numbers in this box, I can get the image down close to 195KB:

S2.png

Now hit OK.

See if that does what you want and post back, please.

Ian
 
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Hi Ian,

Many thanks for getting back to me. The original file was actually 1.4 MB. I got it down to 855 KB by doing exactly what you just tried. Now I have it at the right pixel width and height for the website. However, it is still too large. I read that 72 DPI was the right level for web so don't want to go lower there but maybe that's my only option.

Notice how in your first screen shot, it randomly says '3.4 MB (was 9MB)'. This is the bit I don't understand.

Gavin
 

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Notice how in your first screen shot, it randomly says '3.4 MB (was 9MB)'. This is the bit I don't understand.

The "was xMB" refers to the original photo wherever it came from. In my case, and for the demonstration, I copied a photo from the Photos app to the Desktop, where I opened it with preview. In the copying process, there was some compression.

Basically, you can ignore that figure and concentrate on the current figure (3.4MB in my case).

As regards file size: you can reduce the pixel width further; or the DPI.

Obviously, I don't know where your picture originated, but if it came from an app such as iPhoto, or Photos which has replaced it, you can compress the picture if you copy it to the Desktop first.

Choose File > Export and then you get the chance to change a number of parameters, as in this screenshot:

Screen Shot 2018-05-30 at 14.13.38.png

Try experimenting with Quality and Size.

Hope some of this makes sense:)

Ian
 
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Hi Ian,

Thanks, my dialog box looks a little different to your but I do get a 'quality' slider, which seems to have done the trick. Thanks for your help.

Gavin
 

IWT


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You're very welcome.

I'm still on Sierra and you have High Sierra which probably explains the difference.

Ian
 

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