DEFINITIVE GUIDE TO IMAGEMAGICK PDF

You can tilt the image horizontally and vertically in both directions in other words, from left to right, from right to left, from top to bottom, and from bottom to top. For example, to tilt an image to the right 45 degrees, you use this command line: convert -shear 45 input. In these examples I have also specified a vertical shear of zero. You can also shear vertically by specifying a zero shear angle for the horizontal axis and then a vertical shearing. A positive angle is toward the top of the image, and a negative angle is toward the bottom. For example, to shear vertically toward the top 30 degrees, use this command line: convert -shear 0x30 input.

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You can tilt the image horizontally and vertically in both directions in other words, from left to right, from right to left, from top to bottom, and from bottom to top.

For example, to tilt an image to the right 45 degrees, you use this command line: convert -shear 45 input. In these examples I have also specified a vertical shear of zero. You can also shear vertically by specifying a zero shear angle for the horizontal axis and then a vertical shearing. A positive angle is toward the top of the image, and a negative angle is toward the bottom.

For example, to shear vertically toward the top 30 degrees, use this command line: convert -shear 0x30 input. To perform the shear operation, specify the horizontal and vertical angles as arguments to the shear command-line option. For example, for a horizontal shear of 10 degrees and a vertical shear of 20 degrees, use this command line: convert -shear 10x20 input.

You do this by specifying the horizontal roll and then the vertical roll. To roll just vertically, specify a zero horizontal roll. To roll to the left or upward, use a negative number. This is much more obvious if you set the background color to something a little more obvious than the default of white: convert -background red -append input1.

To do this, just use a plus sign instead of aminus sign as the first character of the append command. These names act as shortcuts to the RGB value associated with that name. You can find out what named colors exist using the following command line: convert -list color This will list the colors that have been defined in the colors. You can represent any color with an RGB value, and this is the color format used by many image formats, as well as a lot of hardware such as computer monitors.

Using RGB Tuples The final method of specifying a color is useful if you know what the decimal values for the various channels you want to set are. Two types of RGB tuples exist. To specify the RGB values, then use this form: rgb value, value, value where value is replaced by the red, green, and blue values, respectively.

Alternatively, if you want to specify an alpha channel as well, then use this form: rgba value, value, value, value Specifying a Page Size For example, to create a new image that is pixels wide and pixels tall and is green, then you use a command line like this: convert -size x xc:green output.

Specifying a Background Color convert -background red -rotate 30 input. This image is filled with the default fill color of black. The image is then saved to output. You can also fill that rectangle with, for instance, light gray. For this command, use a whit background for the image: convert -size x xc:white -stroke green -fill lightgray -draw "rectangle 10,10,,90" output. In this example, the green line is harder to see now that the rectangle is filled. If you make the line 5 pixels wide, then you get amuch more visible border around the fill color: convert -size x xc:white -stroke green -strokewidth 5 -fill lightgray -draw "rectangle 10,10,,90" output.

For instance, in Chapter 4, you saw an example that used the composite command and some corner images to create a curved corner effect on an image. The gravity command told ImageMagick which corner of the large image to place the corner images in. So, the top of the image is North, and the right of the image is East.

You can also specify corners with this compass, in that the top-right corner is NorthEast, for instance. To specify the center of the image, use the Center keyword. You specify the gravity on the command line with the gravity option; for example, to put a rounded corner on the top-right corner of an image, use this command: composite -gravity NorthEast rounded-ne. Note that this inset is the bottom-left corner of the first character, so you expect the text to look closer to the top of the image than it is to the left because of this.

To do this, use the font commandline argument, which takes the name of a font as its argument. The font is stored in the Arbuckle. You also specify another two numbers in the offset specification, which are rotation parameters. You can also specify a box to be placed under the annotation text, which can make it a lot easier to read—in return for being more intrusive on the original image.

You do this by adding the box command-line option to the command, with the argument to the box option being the color of the box. To do this, instead of the annotation text in the command line, use an at sign and then the name of the file containing the annotation text.

This extra argument is the width of the circle and the height of the circle that forms those corners. For example: convert -size x -stroke red -strokewidth 5 -fill lightblue -draw "roundRectangle 10,10 90,90 10,10" xc:white output. The first argument is the center of the circle, and the second argument is how far the circle extends. You can also increase the stroke width of a circle much like a rectangle: convert -size x -stroke red -strokewidth 5 -fill lightblue -draw "circle 50,50 70,70" xc:white output.

You merely specify three pairs of numbers—the first two pairs of numbers are control points that dictate the size of the ellipse in which the arc is drawn. The third pair of numbers is the starting angle of the arc and the ending angle of the arc.

This is a simple command-line example: convert -size x -stroke red -fill lightblue -draw "arc 10,10 90,90 45," xc:white output. The start and end angles are handled the same as in the arc primitive. Bezier curves are based on a series of control points.

To annotate an image using the draw command-line option, use the text primitive, which takes a location and the string to write as arguments. For example, this command writes a word on the blank image: convert -size x -stroke red -draw "text 50,50 blah" xc:white output. Transforming Your Drawings The draw command-line option supports a number of transformations that you can apply to the primitives you use. The rotate command-line option takes an argument that is the number of degrees to rotate clockwise, much like the rotate command-line option discussed in Chapter 6.

Translation is the process of shifting a drawing by a given amount, for example, 40 pixels to the left or pixels down. You just provide a scale primitive with the horizontal scaling factor and vertical scaling factor.

You can perform this skew either horizontally or vertically by using different commands. The following command keeps the stick-figure man blue but makes the text red: convert -fill blue -font Jokerman. If you use 0,0, then the real size of the image is used; any other pair of numbers will result in the image being scaled to the specified size.

The following sections highlight the available operators and show examples of their effects. Using the In Operator The In operator replaces the image data under the overlay image with the overlay image. None of the image data from the original image in the covered area is used, even if the overlay image specifies transparency: convert -draw "image In , , fern. This is no longer the case, however. If the value of two Bits from the input images is different, then the value of the exclusive or operation is a 1.

Otherwise, the value of the exclusive or is 0. This command line: convert -draw "image Xor 50,50 80, fern. The matte channel value is set to opaque. For example: convert -draw "image Plus 50,50 ,80 fern.

For example: convert -draw "image Minus 50,50 ,50 fern. For example: convert -draw "image Difference 50,50 ,90 fern. The ImageMagick documentation suggests that the Difference operator is useful to see differences in similar images. Using the Multiply Operator Multiplymultiplies the pixel value from the input image with the pixel value from the overlay image to determine the value of the pixel in the output image: convert -draw "image Multiply 50,50 ,90 fern.

For example, on LCD monitors, antialiased text often looks fuzzy and slightly out of focus. ImageMagick therefore lets you turn antialiasing on and off.

To use antialiasing, which is the default, just use the antialias command-line option. The way you create one of these frames with ImageMagick is with the frame command-line option. At its most basic, the command takes the thickness of the frame horizontally and vertically as its arguments, like this: convert -frame 10x10 input.

You can specify two other arguments with the frame command-line option. These are the outer bevel width and the inner bevel width.

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ImageMagick - The Definitive Guide To ImageMagick

The final prices may differ from the prices shown due to specifics of VAT rules About this book An open source project backed by years of continual development, ImageMagick supports over 90 image formats and can perform impressive operations such as creating images from scratch, changing colors, stretching, rotating, and overlaying images, and overlaying text on images. Whether you use ImageMagick to manage the family photos or to embark on a job involving millions of images, this book will provide you with the knowledge to manage your images with ease. The Definitive Guide to ImageMagick explains all of these capabilities and more in a practical, learn-by-example fashion. About the authors Michael Still released his first open source project in July and has been actively developing ever since. He has had a variety of articles published by IBM DeveloperWorks, and once made a tux out of fairy lights! Michael grew up in Canberra, Australia, and now works for Google and lives in the Silicon Valley with his wife and two kids.

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The Definitive Guide to ImageMagick

You also specify another two numbers in the offset specification, which are rotation parameters. You can also specify a box to be placed under the annotation text, which can make it a lot easier to read—in return for being more intrusive on the original image. You do this by adding the box command-line option to the command, with the argument to the box option being the color of the box. To do this, instead of the annotation text in the command line, use an at sign and then the name of the file containing the annotation text. This extra argument is the width of the circle and the height of the circle that forms those corners. For example: 1 convert -size x -stroke red -strokewidth 5 -fill lightblue -draw "roundRectangle 10,10 90,90 10,10" xc:white output.

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The Definitive Guide To ImageMagick

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