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"I don't know how to shrink an image!"

Your camera takes really BIG pictures, but you don't know how to shrink them, right? Do you just email them as-is to everyone? Did you know that that can create problems for them, like much longer download times or a full email box that doesn't let other's emails come in? Oops! These instructions are for you! :)

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Perhaps this is all you need

When people make mistakes in shrinking images, it may be because they aren't aware that "size" involves three separate concepts:

  • the resolution of the picture in dots per inch (how many dots of the image can fit within an inch, or "dpi")

I recommend 72 dpi.

  • the width/height of the picture on the screen (typically measured in "pixels" or dots or points)

I recommend no greater than 800x600, typically (and often it is better to have something much smaller, if the details are obvious in the picture).

  • the "quality" setting that is typically offerered at the moment the picture is being saved in JPG format

I recommend a Quality (watch for such a choice while saving the picture in JPG format) about 75-80% of the highest setting. Depending on the software, the Quality value might be called 75% or "8" (out of 10) or "High" (lower than "Maximum").

The most common mistake I have seen is reducing only the Quality when saving the file and leaving the dimensions (width/height) alone (for example, 1024x800 or 2200x 1600). The result is a really "grainy" or "chunky" looking picture.

If you can find how to change these three items in your photo software, you should be on your way to good photo sizes. Don't forget to keep a copy of the original: see "Preserving the original picture."

If you cannot figure out how to change the resolution, dimensions and quality of a picture with your photo software, consider using IrfanView, an excellent, free photo program that can do far more than I describe here (such as create slideshows you can give to friends on CDs). IrfanView is great for the most common, simple photo tasks I describe below, such as rotating, cropping and shrinking images.

Preserving the original picture

Do you want to protect the original, large, clear picture? Perhaps you would prefer to alter a COPY of the original image, in case you make some mistakes?

To make a copy of the original picture file:

1. Open Windows Explorer (Start menu > Programs > Windows Explorer).

2. Find the picture filename on your harddrive in Windows Explorer. (Folder names appear in the left column. Contents of the lefthand folders appear in the righthand column. To open a folder in the lefthand column, click or double-click it.)

3. Right click the picture filename in the righthand column.

4. Right click Copy.

5. Right click anywhere in the righthand column.

6. Right click Paste.

A new file appears at the bottom of the righthand column. It is named "Copy of ..."

7. Give it a better name: Right click the filename, and right click Rename.

The name is highlighted.

8. Type a replacement name that ends with .jpg and press Enter.

You now have a duplicate of the image which you can modify without harming the original.

Opening/viewing an existing picture file with IrfanView

(See "Preserving the original picture" for related thoughts.)

To open a picture in IrfanView:

1. After installing IrfanView once (see "Downloading and installing IrfanView"), start IrfanView (click the Start menu > Programs > IrfanView > IrfanView).

2. Click menu File > Open.

3. Select and open your image from the list. (You may need to select the correct topmost folder from the "Look in" bar at the top of the "Open" window. You may need to double click folder names in the main list in the Open window.)

Finding out how big a picture is

Finding out the dimensions of a picture

1. Open the picture file in IrfanView. See "Opening/viewing an existing picture file with IrfanView."

2. Along the bottom left edge of the IrfanView window are three numbers separated by x's (for example, 1280 x 1280 x 24 BPP).

The first two numbers are the width and height of the picture, measured in pixels (individual color dots). These are the dimensions of the picture.

(Note: Some people call this the "resolution" of the picture, and that creates confusion. The word "resolution" is more often used to mean the clarity or quality of the picture.)

If you are emailing photos, it is kinder to reduce the dimensions below 640 x 480 pixels, because (1) larger images take longer to download and (2) some people have small computer screens and will not see more than 640 x 480 pixels at a time anyway.

3. Along the bottom of the IrfanView window is a percentage, such as 60%.

When this says 100%, you are viewing the picture at its actual size. When you press either the plus ( + ) or minus ( - ) key on your keyboard or keypad, you can look more closely at your picture or move it away from you, but this does not alter the original image (just as using binoculars to view an animal does not change the animal).

Do you want to change the dimensions of an image? See "Reducing the dimensions of a picture."

Finding out the file size (KB) of a picture

If you follow the instructions for "Finding out the dimensions of a picture" above, you will also see two KB numbers along the bottom edge (for example, 120 KB / 1.38 MB). The first number is the size of the picture file on your harddrive. (It is the size that people would receive if you emailed or uploaded the picture.)

Perhaps you have already reduced the dimensions of the picture, but the file size is still larger than you wish? You can reduce file size by reducing image quality, but be sure that that is what you want to do! See "Reducing the file size of a picture."

Reducing the dimensions of a picture

(Before you simply shrink the dimensions of your image, would it be good to trim off unnecessary detail at the edges? See "Cropping a picture.")

To shrink an image:

1. Display the picture in IrfanView. See "Opening/viewing an existing picture file with IrfanView."

2. To determine what a good final size would be, press the plus or minus keys on your keyboard or keypad to see a sample of new size, and read the percentage along the bottom of the screen (for example, 50%).

3. Click menu Image > Resize/Resample.

4. Click the circle for "Set new size as percentage of original" and type the percentage number you saw in the previous step.

5. Click OK.

The image has been changed. If you do not see "100%" along the bottom edge, press the plus or minus keys to get to 100% (which is the new actual size of the image). If you do not like the result, you can undo (menu Edit > Undo) and try again with a different percentage.

Cropping a picture

Cropping a picture is like cutting off its edges with scissors. Cropping keeps only the portion of the picture that is inside of a rectangle that you draw.

1. Display the picture in IrfanView. See "Opening/viewing an existing picture file with IrfanView."

2. Draw a rectangle around the portion of the picture which you wish to keep: click-hold-and-drag the left mouse button to start, and release the button when finished. You can redraw the rectangle as needed.

3. Menu Edit > Crop selection (or press Ctrl-Y).

Reducing the file size of a picture

Many web sites (for example, phoons.com and mirrorproject.com) require that pictures (1) be under a certain width and height and (2) be under a certain KB file size.

Often, if you reduce the dimensions of the picture first (see "Reducing the dimensions of a picture"), the file size will automatically drop to an appropriate level. But what if you want to increase or reduce the file size?

To change the file size of a picture without changing its dimension, change the quality or clarity of the picture. (Why is file size related to picture quality? The lower the quality, the less detail there is in the picture. The less detail, the less information needs to be stored on the harddrive. The less information on the harddrive, the smaller the file size.)

In IrfanView, you control the quality of the image when you save the file:

1. Display the picture in IrfanView. See "Opening/viewing an existing picture file with IrfanView."

2. Click menu File > Save.

3. When the "Save as type" bar shows "JPG- JPEG Files," there is another window that lets you change the "Save quality" of the image.

If you slide this to 100, you get 100% quality. The file size will also be huge.

The more you slide this toward 0, the worse the image will look--but it will be a smaller file size. A lower value of quality means a higher value of compression (compression means reducing detail and file size).

75 or 80 is a good compromise. It keeps the quality high enough for the image to still be nice, and it also helps reduce the file size.

4. Slide it to the quality number you like.

Note: You will NOT see the quality difference in the picture while it is still displayed in IrfanView. You will not see the difference until you open the file again in the future. Some day, read the advanced section on "Issues of saving a picture in JPG format" so you are familiar with problems related to JPGs and quality.

Rotating a picture

1. Display the picture in IrfanView. See "Opening/viewing an existing picture file with IrfanView."

2. Menu Image > Rotate Left (or Rotate Right).

Issues of saving a picture in JPG format

Beware! One kind of saving as JPG will reduce your picture quality. Another kind of saving will NOT. It is important for you to know the difference so that you can be careful in your use of photo software.

Background on picture file formats and JPG

The same picture can be stored on your computer in many different formats. Samples of picture file formats are JPG, GIF and BMP. Why choose one format over another? The GIF and BMP formats preserve the original picture detail. They are typically larger (and even much larger) than the same picture stored in the JPG format. The reason that a JPG file is smaller on your harddrive than the same picture in GIF or BMP format is that a JPG is an approximation of the original detail.

Imagine that you do the following. You save a picture in JPG format and then close the picture window. You then open the picture, save it again in JPG format (with the same filename), and close the picture window. Note that every time you re-open and then re-save in JPG format, the quality of the picture worsens. This is because every new saved JPG result is an approximation of what was opened.

When saving does not reduce the quality further

Imagine you open a picture file in a photo program and then immediately save it in JPG format. The new version of the picture file on the harddrive would be of lower quality than the prior version of the picture file because of the reasons noted in "Background on picture file formats and JPG."

Now imagine that you perform Save another nine times while the same picture is visible in the photo program (without making any visible changes to the picture). There will be no difference in quality between the first saved version of the picture and the tenth saved version. Why is this? Why wouldn't the tenth picture be far worse than the first picture?

The reason is that the JPG approximation is based on the displayed picture, not on the harddrive picture file. Since you did not change the visible picture, each Save is based on that same picture. The first saved picture would therefore have the same approximation as the tenth saved picture because they are both based on the one displayed picture. (The difference from the example noted in "Background on picture file formats and JPG" is that the displayed picture was re-opened several times. The displayed picture matches the re-opened version!)

Copying JPG files

No changes are made to a JPG file simply by copying it from one folder to another or from one filename to another (for example, via Windows Explorer). It is only when you open a JPG file in a photo program and then save with the photo program that JPG approximations are made to the saved version.

Conclusion

Use the JPG format to keep a picture's file size down. Avoid re-opening a JPG file and then saving it. Every time you re-open a JPG file, you begin working with the latest approximated version. It is better to open a picture file once, make many changes to the picture (cropping, shrinking, changing colors and brightness, etc.), and save as often as you wish.

If the JPG format reduces the quality of a picture, should you avoid using it? No! It is a great format for saving because it makes smaller files which are better for emailing and for downloading from websites. However, if it is essential that your picture contain no blurs/errors (for example, a simple button with crisp text on it), the GIF format might be best.

Downloading and installing IrfanView

IrfanView is free. It does MUCH more than these instructions discuss. (For example, you can create web pages with thumbnail images of your photo collection and create a CD with those web pages.)

1. Print out these instructions for future reference.

2. Go to http://www.irfanview.com with your web browser.

3. Click the Download link on the left.

Note the first TWO Tucows items that appear: "IrfanView" and "IrfanView plugins". You will eventually download both of these.

4. Click the first item, "Download IrfanView."

A new browser window appears. (And you will eventually close this window completely to see the prior window.) It has a "Download Now" list with abbreviated versions of Windows operating systems.

5. Click the link that matches your version of Windows.

6. It now lists a bunch of country options. Pick any one of them to continue.

A File Download window appears.

7. Click Save.

Near the top of the Save As window is a picture of a yellow folder with an UP arrow on it.

8. If you do not see "Desktop" as the name to the left of that arrow-folder, re-click that up-arrow-folder until you do.

9. Click the Save button.

This saves a file (for example, iview380.exe) to your Desktop.

10. Close the window that lists the countries (click its upper right X).

12. Now download the second item, "Download IrfanView plugins", the same way.

11. Minimize (or close) all of your windows so that you can find an icon with that filename, and double-click it to begin installation of IrfanView.

12. Whatever the installer shows you, just accept it (click OK or Next or whatever it is) until IrfanView is installed. Do the same for the plugins icon.