How To Use GIMP to Crop and Resize Pictures - Free Software
From Wikipedia:
"The
GNU
Image
Manipulation
Program, or the
GIMP, is a raster graphics editor application with some support for vector graphics. The GIMP can be used to process digital graphics and photographs.
Typical uses include creating graphics and logos,
resizing and cropping photos, changing colors, combining images using a layer paradigm, removing unwanted image features, and converting between different image formats. The GIMP can also be used to create animated images using an improved layers method. The full capabilities of the GIMP extend much further, however, and include advanced image editing, manipulation, and professional graphics creation."
GIMP is provided free of charge under the
GNU General Public License.
Install Program
(For Linux users, see your distribution file/program list. The
GIMP is included with most Linux distributions.)
For Windows users, download and install the desired package from:
GIMP - Windows installers To Crop an Image (image height/width by pixels)
There is no rule that says you must keep your image at the ratio set by your camera! Cropping an image sets the focus point and removes extraneous visual information. Here we will crop the sample image to eliminate some sky.
Original 
Cropped 
There are two methods to crop an image:
1) Set the
Canvas size height and width and move the image into the area
2) Select the desired area with the
Rectangle Select tool (from the
Toolbox floating tool bar)
Crop by Canvas Size
From the menu bar select
Image > Canvas Size..., the
Set Image Canvas Size windows opens.
Click on the chain icon to the right of the
Width and
Height spin buttons to break the link chain - this allows for specific width and height sizes (the link chain sets proportional sizing). Enter your desired width and height.
With your mouse, click on the image and drag it image in the resized box to the desired position. When positioned as you desire, click the
Resize button.
From the menu bar click
Image > Flatten Image.
Name and save your edited image (see
Saving the Image File below).
Crop by Rectangle Select Tool (drag to outline selected area)
From the
Toolbox floating toolbar select the
Rectangle Select Tool.
Start at a desired corner, click and drag the rectangle on the image to define the desired area and release the mouse button.
On the menu bar click
Image > Crop to Selection.
Name and save your edited image (see
Saving the Image File below).
To Scale an Image (image size by pixels)
Open your image from
the GIMP tool window:
File > Open then navigate to your image. Select it (click on it) in the
Name frame then click the
Open button (or double-click on the image name). Your image will open in a new window.
- OR -
Open the
GIMP. Open a
Windows Explorer session and navigate to your image file. Drag and drop the file onto the
GIMP image window.
On the image window menu bar click on
Image > Scale Image. The
Scale Image dialog window will open.
Check that the
Image Size section has a "chain" linking the
Width and
Height boxes (this scales the image proportionally). Check that the value
pixels is displayed (if not, click the drop-list arrow and select
pixels from the list).
> If the Width is the Longest Side (landscape mode), double-click your mouse in the
Width box which will select the value in the box. Type in the desired width.
> If the Height is the Longest Side (portrait mode), double-click your mouse in the
Height box which will select the value in the box. Type in the desired height.
Click the
Quality Interpolation drop-list arrow and select
Cubic (Best) if it is not already selected.
Click the
Scale button.
Your image has been proportionally scaled to your selected value.
Saving the Image File (save to a file size)
The GIMP allows you to save your image and tightly control the file size by selecting a balance of compression "quality", sub-sampling (part of the compression calculation), "smoothing" and other advanced options (such as saving EXIF data and including a thumbnail image). This short How-To will not explain these setting but will give preferred setting to maximize image quality within a maximum file size value.
On the image window menu bar click on
File > Save as... The
Save Image dialog window opens.
> If you are NOT working with a JPEG (jpg) image but want to save as a JPEG (jpg), click the "
+" in front of
Select File Type (By Extension) and scroll down the
File Type and select (click on)
JPEG image.
Click your mouse in the
Name box and type in the name of the file (do not include the .jpg extension).
> Note the location of the
Save in folder so you can find your image or click the
Save in folder drop-list arrow and navigate to the location where you want to save the file.
Click the
Save button. The
Save as JPEG dialog window opens.
Click (check) the box in front of
Show Preview in image window. After checking the box you will see the
File size displays with the current
Advanced Options selections and values (displayed above the
Show Preview in image window check box).
Click the "
+" in front of
Advanced Options. The
Advanced Options expands with program default values.
Preparation to set quality and smaller file size:
> check
Optimize
> check
Progressive (some sites may not like this setting)
> uncheck
Save EXIF data
> uncheck
Save thumbnail
> set the
DCT method to
Integer or
Floating-Point from the drop-list
From here you need to experiment with several values to balance image quality with file size. Changing a value will change the file size; some settings yield larger file size changes over other settings. The
Save as JPEG window shows the
File size on the top left just below the
Quality slider.
Begin at the top of the
Save as JPEG dialog window by changing the
Quality value. Move the slider or click on the up/down spin buttons to change the
Quality value until the
File size is just above or just below the desired file size.
Next decide on a
Sub-sampling value (select the value from the drop-list):
>
2x2,1x1,1x1 yields the smallest file size because of highest compression formula (most affect on the image)
>
2x2,1x1,1x1 (4:2:2) yields a slightly larger file size with a little less compression formula (more affect on the image)
>
1x1,1x1,1x1 yields the largest file size with the least compression formula (least affect on the image)
Re-adjust the
Quality value (at the top of the window) - the goal is a high
Quality value with an acceptable sub-sampling algorithm. You can exceed the desired limit by .2kb (point 2kb) and then use the
Smoothing setting to lower the file size BUT THIS WILL SOFTEN THE IMAGE slightly. Click the UP spin button to increase the smoothing by 0.01 per click. Do not exceed a value of 0.10 or the image will become too soft - unless you are softening deliberately (but there are better ways to do that). You can watch the
Smoothing effect on the image as you change values (it will preview the image as you make changes).
Click the
Save button.
Final image, cropped and sized 
(If you find errors or confusing information, please PM me and I'll make revisions.)
Regards,
GEWB
Linear Mode
