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Author Topic: Grabbing an image, down-and-dirty  (Read 7921 times)
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rlb
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« on: Dec 05, 2007, 08:20PM »

A contribution from our very own Mr. Play_Louder this time:



We’ve had various people staying at our place recently, and of course they have all been taking lots of photos of Sydney (average is 25 of the opera house and about 50 of the bridge!). Many of our visitors then want to upload them to facebook, email them etc.

With modern digital cameras typically producing images of 4 or 5 MB, however, this process can become rather slow, even on a fast broadband connection. However, I have noticed that very few people actually understand why, or know how to make it much faster.

I’ve therefore shown several people the following process for making images more suitable to email / web upload; the beauty of doing it this way (even it if seems a bit cack-handed) is that it needs no additional software other than stuff Windows ships with – so can be done even in an internet café in whoop whoop.

Before we get to that, though, here’s some theory on image sizes. Feel free to skip this bit and just jump to the recipe if you aren’t interested!

How big is an image?
Images are made up of lots of dots (pixels), and the size (as in how much room it takes up on your PC hard disk) of an electronic image is related to the number of pixels in the image. The total number of pixels in an image is the number of pixels across the top multiply the number down the side. So if your image is 800 pixels wide and 600 high, it will have 480,000 pixels. (One ‘megapixel’ is one million pixels – so a ‘6 megapixel camera’ will produce images with around 6,000,000 pixels per image.) An image with more pixels is generally ‘higher resolution’, ie will show a greater level of detail / be higher quality.

Because the total size is two numbers multiplied together, even what seems like quite a modest increase in resolution leads to a big increase in the number of pixels. If we increase the resolution of our image from 800x600 to 1600x1200, we get nearly 2 million pixels – a 4 fold increase in size, even though it is only twice as wide. (For the mathematically minded, the number of pixels increases with the square of the width). As the final size of the image on the computer is related to the number of pixels, rather than the width, it leads to the size quickly becoming enormous as the resolution gets finer.

How many pixels do I need?
The number of pixels you need in an image depends on what you intend to do with it. When viewing an image (whether on a screen or printed out), the quality is related to the number of pixels per inch of image. In printing terms, this is called dots per inch (dpi) and printers are usually specified in this way. If you print out an 800x600 image so that it is 4 inches wide, the dpi will be 200 (as there will be 200 pixels per inch of image). The higher the dpi, the better quality the image will appear.

The important point is that the image only has to have enough pixels to deliver the required dots per inch. If the image has more pixels than can be printed / displayed, then the extra resolution will be wasted.

So the resolution you need is related to what you want to use the image for. Here are some common dots per inch:

72 – 96 dpi – this is how many pixels per inch a computer screen typically displays
150 dpi – this is typical for colour newsprint pictures
300 dpi – typical for glossy magazines
450 dpi – as good as most photos
600 dpi – basically indistinguishable from high quality photos

You can use this table to determine the number of pixels you need in your image. For example, say I wanted to print out a picture as a 6x4 print, photo quality. I might want 450dpi – so if the image is 6 inches across I need 6x450 = 2700 pixels across. That’s going to mean I need pretty much all of my 6MP camera image. So when taking  / printing photos for your album, it’s probably best to go with the best image resolution you can.

But what if I just want to print out a quick snap to pin on the fridge for a few days? Something closer to a newspaper print would do fine for that – so I’d only need 150 dpi. For the same size image that’s only 900 pixels across. In size, then, that picture is only a tenth of the size of the one in the last example.

How about if I just want to put the pic on facebook for people to look at on a screen? Screens have a low dpi – lets assume 96dpi. Assuming on the screen the picture will come up around 6 inches across, that’s 6x96 = 570 pixels across. That’s only 5% of the size of the image we needed for a quality print. Or to put it another way; if I were to upload the full picture to my blog it would take 20 times longer than the smaller version, but people viewing it wouldn’t see any difference in quality (as the quality is limited by their screen).

In my experience most people who email / upload pictures are only doing so with an expectation that they will be viewed on a screen. So sending the full file from your camera is generally not necessary; it takes longer, fills up people’s inboxes and can be less reliable (some email services reject such large emails).

Reducing the image size
But how do I make the image smaller? Well, you can open the image in your favourite image software, and find the ‘resize’ function, and generally just type in the size you’d like to have. But what if you don’t have any image software, or are on someone else’s PC?

Here’s a quick and dirty way to get images down to a size that’s suitable for emailing / uploading (using a Windows PC).
1) Open the image by double clicking on it. It will open in ‘preview’.
2) You then make the image ‘full screen’ by clicking the ‘slideshow’ button under the image. The image should now fill the screen completely.
3) Press the ‘Print Screen’ (Prt Scr) – on a standard keyboard it’s next to the F12 key – on a laptop it’s usually someone up on the top right.
4) Press ‘Esc’ to exit the image preview
5) Open ‘paint’ – you can find it in the start menu under ‘all programs’ -> ‘accessories’
6) Do paste – either hold down Ctrl and press ‘v’, or select ‘paste’ from the file menu
7) If a dialog box pops up, click OK.
8) You should now see the image in paint.
9) Select ‘Save as’ from the file menu
10 Give the file whatever name you want, and make sure you select ‘JPEG’ in the ‘save as type’ dropdown (under where you put the name)

That’s it! Sounds like a lot of effort, but once you are used to it it only takes about 10 seconds. And you’ll save a lot more than 10 seconds uploading the resulting picture to your blog vs the original!
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« Reply #1 on: Dec 05, 2007, 08:33PM »

Another really easy option is this

1: open pic with Microsoft Picture Manager
2: Go to the "Pictures" tab and select "Compress Pictures"
3: Pick the compression option relevant to your desired size
4: Save (you probably want to save it as a copy, to keep the high quality original)
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play_louder

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« Reply #2 on: Dec 21, 2007, 08:44PM »

For those who are wondering, here's a similar quick and dirty way to do it on an apple mac.

1) Open the image in 'preview' - usually just double clicking on it will do this.

2) Resize the window to fit most of the screen, then select the 'zoom to fit' function (on toolbar or in 'view' menu).

3) Go to the 'File' menu and select 'Grab' and 'Selection'

4) Put the cursor at the top corner of the image, and drag it down to the bottom corner - then let go of the mouse.

5) If the 'drawer' does not appear, press the 'drawer' button on the toolbar or select 'drawer' from the 'view' menu

6) In the drawer at the bottom you should see an image called something like 'snapshot 2007-01-01'. Click on it. You should now see your image in the main screen.

7) Select 'save as' from the 'file' menu, and select 'JPEG' for the format. That's it!

Doing this also leaves a copy of the image (the one labelled 'snapshot xxx-xx-xx') on the desktop, so you might want to delete it when you've finished.
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rjs18
« Reply #3 on: Jun 08, 2008, 09:01PM »

For those who are wondering, here's a similar quick and dirty way to do it on an apple mac.

1) Open the image in 'preview' - usually just double clicking on it will do this.

2) Resize the window to fit most of the screen, then select the 'zoom to fit' function (on toolbar or in 'view' menu).

3) Go to the 'File' menu and select 'Grab' and 'Selection'

4) Put the cursor at the top corner of the image, and drag it down to the bottom corner - then let go of the mouse.

5) If the 'drawer' does not appear, press the 'drawer' button on the toolbar or select 'drawer' from the 'view' menu

6) In the drawer at the bottom you should see an image called something like 'snapshot 2007-01-01'. Click on it. You should now see your image in the main screen.

7) Select 'save as' from the 'file' menu, and select 'JPEG' for the format. That's it!

Doing this also leaves a copy of the image (the one labelled 'snapshot xxx-xx-xx') on the desktop, so you might want to delete it when you've finished.

It works I am a Mac user and I do that sometimes
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Magnum
« Reply #4 on: Nov 03, 2009, 02:16PM »

also consider the Free (and spyware free) small program IRFanView. Its useful enough as a picture viewer, converter that I always keep a copy on my "important stuff" thumbnail drive.

If you have multiple pictures to convert, this will do it for you fast.  Once you have the program installed, select Batch Convert.  Not only will it resize pictures, but convert from 1 format to the other.  And you can do all those 100 pictures in 1 easy step.

I'll post a step by step guide when i get a chance.
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