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Resize Images - Your Choices (Four)
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Scale & Rotate Tools GIMP
Scale Image Command GIMP Crop Tool GIMP
Set Image Canvas Size Command GIMP

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This GIMP (GNU) tutorial demonstrates how to reduce an image’s size using either the Crop Tool, or the Scale And Rotate Tools, or the Scale Image Command or the Set Image Canvas Size Command.

The Canvas Size is the visible area of the image. By default the size of the canvas coincides with the size of the Layers. The Canvas Size command lets you enlarge or reduce the canvas size without modifying the contents of the Layers in the image. When you enlarge the canvas, you create free space around the contents of the image. When you reduce it, the visible area is cropped, however the Layers still extend beyond the canvas border.

Sharpen Images
Create A Fill Layer
Optimise And Save Images
Utilise The Rotate Tool To Straighten Horizons

Table Of Contents
Utilise The Shear Tool
Resize Images Using The Crop Tool
Resize Images Using The Scale Image Command
Resize Images Using The Scale And Rotate Tools
Resize Images Using The Set Image Canvas Size Command

The Crop Tool
To work along, you are welcome to download the Start Image I am working with
Here. Unzip the file and open the image onto GIMP’s workspace.

Note
Photographs will always react uniquely, therefore, for personal results, experiment with different Resizing options and discover a technique that works best for you.

Notes
You can quickly Undo a step at any time by pressing Ctrl then Z. Alternatively, click a previous Undo History snapshot - Windows then Dockable Dialogues then click Undo History. In addition, to Zoom in (or Zoom out) of your image; from the top menu, choose View then select a Zoom Tool from the subsequent drop-down list.

Understand GIMP’s Toolbox
Launch GIMP & Organise Its Workspace & Palettes

1/
Open your Start Image onto GIMP’s workspace - File then Open - Ctrl then O.

Note
Ensure the Layers and the Undo History Palettes are visible, and then drag them into position over your workspace - (Windows then Dockable Dialogues - then click Layers and Undo History)
.



One way of reducing a photograph’s size is by implementing the Crop Tool. To activate the Crop Tool, from the left-side Toolbox, left-click the following Crop Tool tab.



Then left-click and drag out a Rectangular Shaped Bounding Box around the area you want to retain - as illustrated below. 



As soon as you release the mouse button, you will see Four Square Shaped Repositioning Handles attached to the The Crop Bounding Box - as illustrated below.

Note
You may need to hover your cursor over your image to see the Square Repositioning Handles.



Tip
If necessary, you can Reposition the Crop Bounding Box by gently tugging one of the Square Repositioning Handles.



Tip Cancel The Crop Tool
To cancel the Crop Tool, click any other Toolbox Tool - perhaps the Move Tool.

Reposition The Bounding Box
To reposition the Crop Bounding Box pixel-by-pixel - tap one of the following Keyboard Arrow Keys



When you have surrounded an area you wish to retain with a Rectangular Shaped Crop Bounding Box: left-click inside the Bounding Box to commit the Crop. Alternatively, tap your Enter/Return Key to commit the Crop.

Your photograph will then be Cropped to the Crop Bounding Box’s size, as illustrated below.



Congratulations, your image has been resized using the Crop Tool
and it is ready to optimise and save.

Sharpening Images
After Resizing an image, it’s good practise to apply a
Sharpening Filter afterwards. (Filters then Enhance, then select either Sharpen or Unsharp Mask).

The Set Image Canvas Size Command
To work along, you are welcome to download the Start Image I am working with
HereUnzip the file and open the image onto GIMP’s workspace.

Note
Photographs will always react uniquely, therefore, for personal results, experiment with different Resizing options and discover a technique that works best for you.

Notes
You can quickly Undo a step at any time by pressing Ctrl then Z. Alternatively, click a previous Undo History snapshot - Windows then Dockable Dialogues then click Undo History. In addition, to Zoom in (or Zoom out) of your image; from the top menu, choose View then select a Zoom Tool from the subsequent drop-down list.

Launch GIMP & Organise Its Workspace & Palettes

1/
Open your Start Image onto GIMP’s workspace - File then Open - Ctrl then O.

Note
Ensure the Layers and the Undo History Palettes are visible, and then drag them into position over your workspace - (Windows then Dockable Dialogues - then click Layers and Undo History)
.



Then from the top menu, choose Image then choose Canvas Size. And from the subsequent Set Image Canvas Size dialogue box - experiment with different measurements and settings to see how they effect your photograph. When you are happy with your settings, click the Resize tab.



Width And Height
You can set the Width and the Height of the canvas. The default units are pixels but you can choose different units, for example, percent, if you want to set the new dimensions relative to the current dimensions. If the Chain to the right of the Width and Height is not broken, both Width and Height keep the same relative size to each other. That is, if you change one of the values, the other one also changes a corresponding amount. If you break the Chain by clicking on it, you can set Width and Height separately. Whatever units you use, information about the size in pixels and the current resolution are always displayed below the Width and Height fields. You cannot change the resolution in the Canvas Size dialogue; if you want to do that, use the Print Size dialogue.

Offset
The Offset values are used to place the image on the canvas. The preview window displays the image in a frame with a thin border. When the canvas is smaller than the image, the preview window shows it in a frame with a thin black border. X; Y The X and Y parameters specify the co-ordinates of the upper left corner of the image relative to the upper left corner of the canvas. When the canvas is smaller than the image, the X and Y values are negative. You can change these values by using the text boxes. The default units are pixels, but you can choose different units. By clicking on the arrows next to the text boxes, you can move the image one pixel at a time. You can move the image ten pixels at a time by clicking on the arrows while pressing the Shift Key.

Centre
The Centre button allows you to centre the image on the canvas. When you click on the Centre button, the offset values are automatically calculated and displayed in the text boxes.

Note
When you click on the Resize button, the canvas is resized, but the pixel information and the drawing scale of the image are unchanged. If the Layers of the image did not extend beyond the borders of the canvas before you changed its size, there are no Layers on the part of the canvas that was added by resizing it. Therefore, this part of the canvas is transparent and displayed with a chessboard pattern, and it is not immediately available for painting. You can either Flatten the image, in which case you will get an image with a single layer that fits the canvas exactly, or you can use the Layer to Image Size command to resize only the active Layer, without changing any other Layers. You can also create a New layer and fill it with the
background you want.

Congratulations, your image has been resized using the Set Image Canvas Command -
and it is ready to optimise and save.



Sharpening Images
After Resizing an image, it’s good practise to apply a
Sharpening Filter afterwards. (Filters then Enhance, then select either Sharpen or Unsharp Mask).

The Scale Image Command
The Scale Image command enlarges or reduces the physical size of the image by changing the number of pixels it contains. It changes the size of the contents of the image and resizes the canvas accordingly. It operates on the entire image. If your image has Layers of different sizes, making the image smaller could shrink some of them down to nothing, since a layer cannot be less than one pixel wide or high. If this happens, you will be warned before the operation is performed.

Note
Photographs will always react uniquely, therefore, for personal results, experiment with different Resizing options and discover a technique that works best for you.

To work along, you are welcome to download the Start Image I am working with
HereUnzip the file and open the image onto GIMP’s workspace.

Notes
You can quickly Undo a step at any time by pressing Ctrl then Z. Alternatively, click a previous Undo History snapshot - Windows then Dockable Dialogues then click Undo History. In addition, to Zoom in (or Zoom out) of your image; from the top menu, choose View then select a Zoom Tool from the subsequent drop-down list.

Launch GIMP & Organise Its Workspace & Palettes

1/
Open your Start Image onto GIMP’s workspace - File then Open - Ctrl then O.

Note
Ensure the Layers and the Undo History Palettes are visible, and then drag them into position over your workspace - (Windows then Dockable Dialogues - then click Layers and Undo History)
.



Now, from the top menu, choose Image then choose Scale Image. And from the subsequent Scale Image dialogue box - experiment with different measurements and settings to see how they effect your photograph. When you are happy with your settings, click the Scale tab. 

Note
You are looking to clear the Width and Height boxes, and type in new values of your choice - as illustrated below.
 


For most image resizing, I find the best Quality (Interpolation) setting is Cubic: however, experiment, and find a Quality Interpolation setting that suit’s your image’s requirements.

    

Width And Height
When you click on the Scale command, the dialogue displays the dimensions of the original image in pixels. You can set the Width and the Height you want to give to your image by adding or removing pixels. If the chain icon next to the Width and Height boxes is unbroken, the Width and Height will stay in the same proportion to each other. If you break the chain by clicking on it, you can set them independently, but this will distort the image. However, you do not have to set the dimensions in pixels. You can choose different units from the drop-down menu. If you choose percent as the units, you can set the image size relative to its original size. You can also use physical units, such as inches or millimetres. If you do
that, you should set the X resolution and Y resolution fields to appropriate values, because they are used to convert between physical units and image dimensions in pixels.

X Resolution And Y Resolution
You can set the printing resolution for the image in the X resolution and Y resolution fields. You can also change the units of measurement by using the drop-down menu.

Quality (Interpolation)
To change the image size, either some pixels have to be removed or new pixels must be added. The process you use determines the quality of the result. The Interpolation drop down list provides a selection of available methods of interpolating the colour of pixels in a scaled image:
Interpolation
    
None
No interpolation is used. Pixels are simply enlarged or removed, as they are when zooming. This method is low quality, but very fast.

Linear
This method is relatively fast, but still provides fairly good results.

Cubic
The method that produces the best results, but also the slowest method.

Sinc (Lanczos 3)
New with GIMP-2.4 - this method gives less blur in important resizings.

Sharpening Images
After Resizing an image, it’s good practise to apply a
Sharpening Filter afterwards. (Filters then Enhance, then select either Sharpen or Unsharp Mask).

The Scale And Rotate Tools
To work along, you are welcome to download the Start Image I am working with
HereUnzip the file and open the image onto GIMP’s workspace.

The Scale Tool is used to Scale Layers, Selections or Paths (the Object).
When you click on image with the tool the Scaling Information dialogue box is opened, allowing to change separately Width and Height. At the same time a Preview (possibly with a grid or an outline) is superimposed on the object and handles appear on corners and borders that you can click and drag to change dimensions. A small circle appears at centre of the Preview allowing to move this preview.

Note
Photographs will always react uniquely, therefore, for personal results, experiment with different Resizing options and discover a technique that works best for you.

Notes
You can quickly Undo a step at any time by pressing Ctrl then Z. Alternatively, click a previous Undo History snapshot - Windows then Dockable Dialogues then click Undo History. In addition, to Zoom in (or Zoom out) of your image; from the top menu, choose View then select a Zoom Tool from the subsequent drop-down list.

Launch GIMP & Organise Its Workspace & Palettes

1/
Open your Start Image onto GIMP’s workspace - File then Open - Ctrl then O.

Note
Ensure the Layers and the Undo History Palettes are visible, and then drag them into position over your workspace - (Windows then Dockable Dialogues - then click Layers and Undo History)
.



Then from the left-side Toolbox, activate the Scale Tool - Shift then T.



Now, left-click over your image, and you will then see the following Scale dialogue box.



In addition, your image will now be surrounded by the following Transformation Bounding Box. And you will notice it has Eight Outer and One Central Repositioning Handles attached to it - as illustrated below.



To reduce your photograph’s size: left-click over the top-right Repositioning Handle, and drag it diagonally towards the bottom-left corner. This reduces the Transformation Box’s size, and in turn reduces your photograph’s size - as illustrated below.

Ctrl Tip
If you hold down the Ctrl Key as you reposition the Handle, your image will be rescaled in proportion.



To commit the rescale, click the following Scale tab. Alternatively, tap your Enter/Return Key.





To Rotate your image: from the left-side Toolbox, activate the Rotate Tool.



And then hover your cursor over your image, and you will see the following Rotate icon.



Now, left-click and swivel your mouse in an upwards and downwards movement.



After you have rotated your image, click the Rotate tab to commit the rotation.
Alternatively, tap your Enter/Return Key. (
The Rotate Tool To Straighten Horizons).

To Reposition your rotated image: first, activate the Move Tool .

And then grab the Central Moving Handle, and drag your image to a different position.



Move The Bounding Box Tip
To move your image, ensure the Move Tool is active .

And then tap your image into position pixel-by-pixel by tapping one of the following Keyboard Arrow Keys



Utilise The Shear Tool
(Continue With Tutorial Here)
The
Shear Tool is used to shift one part of an image, a Layer, a Selection or a Path to a direction and the other part to the opposite direction. For instance, a horizontal shearing will shift the upper part to the right and the lower part to the left. A rectangle becomes a diamond. This is not a rotation: the image is distorted. To use this tool after selecting, click on the image or the selection: a grid is possibly superimposed and the Shearing Information dialogue is opened. By dragging the mouse pointer on the image you distort the image, horizontally or vertically according to the direction given to the pointer. When you are satisfied, click on the Shear button in the info dialogue to validate.

From the left-side Toolbox, activate the Shear Tool.



Then left-click and swivel your image to a Sheared position, as illustrated below.



And commit the Shear by clicking the following Shear tab.





Tutorial Continued
Now, activate the Crop Tool.
 


And crop away extraneous background pixels - as demonstrated at the beginning of this
Resizing Tutorial Here

Drop Shadow Tip
My
Tutorial Here demonstrates how to apply a Drop Shadow - Filters then Light and Shadow then Drop Shadow.

Fill Layer Tip
My
Tutorial Here demonstrates how to Fill the Transparent Background with either a Solid Colour, Pattern or a Gradient.

Congratulations, your image has been resized using the Scale and Rotate Tool,
and it is ready to optimise and save.



Sharpening Images
After Resizing an image, it’s good practise to apply a
Sharpening Filter afterwards. (Filters then Enhance, then select either Sharpen or Unsharp Mask).

Now you are more familiar with GIMP’s Resizing options, take a little time to familiarise yourself with them and in no time, you’ll be resizing images without giving it a second thought.

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