Difference between revisions of "Documentation/OOo3 User Guides/Calc Guide/Modifying images"

Revision as of 15:08, 13 December 2010

When you insert a new image, you may need to modify it to suit the document. This section describes the use of the Picture toolbar, resizing, cropping, and a workaround for rotating a picture. Changes made in Calc do not affect the original picture, whether it is embedded or linked.

Calc provides many tools for working with images. These tools are sufficient for most people's everyday requirements. However for professional results it is generally better to use an image manipulation program such as GIMP to modify images (for example, to crop, resize, rotate, and change color values) and then insert the result into Calc. GIMP is an open-source graphics program that can be downloaded from http://www.gimp.org/downloads/.

Using the picture toolbar

When you insert an image or select one already present in the document, the Picture toolbar appears. You can set it to always be present (View > Toolbars > Picture). Picture control buttons from the Picture toolbar can also be added to the Standard Toolbar. See Setting Up and Customizing Calc for more information.

This toolbar can be either floating or docked. Figure 4 shows what the Picture toolbar looks like when it is floating. A brief explanation of the function of the tools is given in Table 1. A more detailed exploration is provided in the Draw Guide.

Two other toolbars can be opened from this one: the Graphic Filter toolbar, which can be torn off and placed elsewhere on the window, and the Color toolbar, which opens as a separate floating toolbar.

From these toolbars, you can apply small corrections to the graphic or obtain special effects.

The Picture Toolbar

Table 1: Picture toolbar functions (from left to right)

Icon	Name	Behavior
	From File	Use of this icon is described in Inserting an image from a file.
	Filter	Displays the Graphic Filter toolbar.
	Graphics Mode	The drop-down list reveals several color modes.
	Color	Opens the Color toolbar.
	Transparency	Sets the transparency of the selected image.
	Line	Adjusts the border style of the selected image.
	Area	Fills an area with the selected color or pattern.
	Shadow	Adds a drop shadow to the edges of the picture.
	Crop	Opens the Crop dialog, where you can remove a selected part of the picture.
	Anchor	Toggles between anchoring the image to the cell or to the page.
	Bring to Front	Brings the selected image to the front of the stack.
	Send to Back	Pushes the selected image to the rear of the stack.
	To Foreground / Background	Allows image to float in the foreground or makes it part of the background (behind the cells).
	Alignment	If two or more pictures are selected, adjusts the horizontal and vertical alignment of the pictures in relation to each other.

Choosing a graphics mode

You can change color images to grayscale by selecting the image and then selecting Grayscale from the Graphics mode list.

Table 2: Graphics modes

Using graphic filters

Click the Filter icon to display the Graphic Filter toolbar, which provides options for applying basic photographic and effect filters to images from within Calc. To "tear off" this toolbar and place it anywhere on the screen, click on the three parallel lines and drag it away.

The graphic filters available in Calc

Table 3: Graphic filters and their effects

Icon	Name	Behavior
	Invert	Inverts the colors in the picture like a negative.
	Smooth	Applies a Gaussian Blur to the image which softens edges.
	Sharpen	Sharpens the image.
	Remove Noise	Applies crude noise reduction.
	Solarization	Reverses a portion of the tones, then produces pronounced outlines of the highlights.
	Aging	Applies a Sepia filter.
	Posterize	Opens a dialog to determine the number of poster colors. This effect is based on the reduction of the number of colors. It makes photos look like paintings.
	Pop Art	Applies a Pop Art style to the image.
	Charcoal Sketch	Applies a Charcoal Sketch look to the image.
	Relief	Displays a dialog for creating reliefs. The position of the imaginary light source that determines the type of shadow can be chosen.
	Mosaic	Joins small groups of pixels into rectangular areas of the same color. The larger the individual rectangles are, the fewer details the graphic image has.

Applying OOo picture filters to any image consecutively will progressively degrade the quality of the image. The picture filters used in Calc utilize what is known as a Destructive Editing algorithm, whereby each filter is applied to the image immediately, changing the original data of the image. Successive transformations result in less and less original data remaining, thus compromising the quality of the inserted picture. While this might be acceptable for use in simple documents, it is still recommended that dedicated photo or image editing software be used to perform anything but the simplest of manipulations.

Adjusting colors

Use the Color toolbar to adjust an image’s red, green, and blue channels independently, as well as its brightness, contrast and gamma.

The Color Toolbar

Setting transparency

Modify the percentage value in the Transparency box on the Picture toolbar to make the image more transparent. This is particularly useful when creating a watermark or when wrapping the image in the background.

Customizing lines, areas, and shadows

The Line, Area, and Shadow icons opens dialogs where you can customize them. Details are in the Draw Guide.

Cropping pictures

When you are only interested in a section of the image for the purpose of your document, you may wish to crop (cut off) parts of it. The user interface in Calc for cropping an image is not very friendly. so it may be a better choice to use a graphics package.

Click the Crop icon to open a dialog where you can select which portion of the image you want to remove.

It is not possible to use the mouse to select the area to be cropped, as you can in Draw. Instead, in the Crop dialog, specify how far from the top, bottom, left and right borders the crop should be, as illustrated below. On the thumbnail in the figure, notice that the cropped selection is highlighted with an inner rectangle.

The Crop dialog

On the Crop dialog, you can control the following parameters:

Keep scale / Keep image size

When Keep scale is selected (default), cropping the image does not change the scale of the picture.

When Keep image size is selected, cropping enlarges (for positive cropping values), shrinks (for negative cropping values), or distorts the image so that the image size remains constant.

Left, Right, Top, and Bottom

The image is cropped by the amount entered in these boxes. For example, a value of 3cm in the Left box cuts 3 cm from the left side of the picture.

• When Keep scale is selected, the size of the image also changes, so in this example the width will be reduced by 3 cm.
• When Keep image size is selected, the remaining part of the image is enlarged (when you enter positive values for cropping) or shrunk (when you enter negative values for cropping) so that the width and height of the image is not changed.

Width and Height

The Width and Height fields under either Scale or Image size change as you enter values in the Left, Right, Top, and Bottom fields. Use the thumbnail next to these fields to determine the correct amount by which to crop.

The cropped shape is always a rectangle; more complex cropped shapes are not possible in Calc. Instead, use a dedicated photo or image editing software for the job, then import the image into Calc.

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Resizing an image

To resize an image.

1. Click the picture, if necessary, to show the green resizing handles.
2. Position the pointer over one of the green resizing handles. The pointer changes shape giving a graphical representation of the direction of the resizing.
3. Click and drag to resize the picture.
4. Release the mouse button when satisfied with the new size.

The corner handles resize both the width and the height of the graphic object simultaneously, while the other four handles only resize one dimension at a time.

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Resizing a bit-mapped (raster) image such as a photograph adversely affects the resolution, causing some degree of blurring. It is better to use a graphics package to size your picture correctly before inserting it into your document, if possible.

For more accurate resizing, use the Position and Size dialog.

Rotating a picture

Calc does not provide a tool for rotating a picture, but you can use this workaround:

1. Open a new Draw or Impress document.
2. Insert the image you want to rotate.
3. Select the image, then in the Drawing toolbar (shown by default at the bottom of the window in Impress and Draw), select the Rotate icon .
4. Rotate the image as desired. Use the red handles at the corners of the picture and move the mouse in the direction you wish to rotate. By default the picture rotates around its center (indicated by a black crosshair), but you can change the pivot point by moving the black crosshair to the desired rotation center. To restrict the rotation angle to multiples of 15 degrees keep the Shift key pressed while rotating the image.
5. Select the rotated picture by pressing Ctrl+A, then copy the image to the clipboard with Ctrl+C.
6. Finish by going back to the Calc document, place the cursor where the image is to be inserted, and press Ctrl+V.