Common Tasks |
Converting an image to another format is as simple as writing the image to a file. ImageMagick uses the output filename suffix (".jpg" for JPEG, ".gif" for GIF, for example) or prefix ("ps:" for PostScript, for example) to determine the format of the output image.
img = Image.new "bigimage.gif" thumb = img.scale(125, 125) thumb.write "thumb.gif"
Alternatively, just pass a single Float
argument that represents the change in size. For example, to
proportionally reduce the size of an image to 25% of its
original size, do this:
img = Image.new "bigimage.gif" thumb = img.scale(0.25) thumb.write "thumb.gif"
The resize method gives you more control by allowing you to specify a filter to use when scaling the image. Some filters produce a better-looking thumbnail at the expense of extra processing time. You can also use a blur argument, which specifies how much blurriness or sharpness the resize method should introduce.
Finally, the sample method, unlike the other two, does not do any color interpolation when resizing.
Here's one way to make a drop shadow behind text. Use the gaussian_blur method to blur a light gray copy of the text, position the "shadow" slightly to the right and down, then draw the foreground text slightly to the left and up. (Click the image to see the Ruby program that created it.)