[img_border/] resizes the source image by adding pixels to the edges. Width values should be positive integers. The color of the border is specified as RGB values in the parameters color_r, color_g, and color_b. If Imagick is available, border opacity can be adjusted using color_a, setting a value between 0.0 (transparent) and 1.0 (opaque).
[img_border output="{format}" top="{int}" left="{int}" bottom="{int}" right="{int}" color_r="{0-255}" color_g="{0-255}" color_b="{0-255}" color_a="{0-1.0}"]<source>[/img_border]dimensions
[img_border output="img" top="20" left="20" bottom="20" right="20"]atest.gif[/img_border]
<img src="/wp-content/uploads/image-cache/1d2cf16c/atest_gif/border_20_20_20_20_00000000.gif" width="212" height="283" alt="atest.gif" />
colors
[img_border output="img" top="20" left="20" bottom="20" right="20" color_r="0" color_g="100" color_b="255" color_a="0.6"]atest.gif[/img_border]
<img src="/wp-content/uploads/image-cache/1d2cf16c/atest_gif/border_20_20_20_20_0064ff06.gif" width="212" height="283" alt="atest.gif" />