NAME

imdisp_pos -- Determine the location of an image within the image display.

USAGE

imdisp_pos image

DESCRIPTION

This task is used to determine the viewport coordinates needed when specifying a viewport on the image display so that it will cover the image. This is necessary because the graphics I/O (GIO) and the image display tasks lack communication.

PARAMETERS

image [file name]

The image specified for the image display task. The syntax used to specify this parameter should be exactly the same as that used in the image parameter in the images.tv.display task.

(left = INDEF) [real]

This is a task parameter that will return the left side of the viewport where the image is displayed.

(right = INDEF) [real]

This is a task parameter that will return the right side of the viewport where the image is displayed.

(bottom = INDEF) [real]

This is a task parameter that will return the bottom side of the viewport where the image is displayed.

(top = INDEF) [real]

This is a task parameter that will return the top side of the viewport where the image is displayed.

(section = "") [string]

The modified image specification containing the section of the image that actually appears in the display.

EXAMPLES

In the following examples, the display is configured for a 512x512 frame buffer.

1. Determine where a 300 x 300 image is located in the display:

cl> images
im> tv
tv> stsdas
st> playpen
pl> display image300 1
pl> imdisp_pos
pl> lpar imdisp_pos
image = "image300" Displayed image specification
(left = 0.2074363976717) Left side of viewport, NDC
(right = 0.79256361722946) Right side of viewport, NDC
(bottom = 0.2074363976717) Bottom side of viewport, NDC
(top = 0.79256361722946) Top side of viewport, NDC
(section = "image300[1:300,1:300]") Section actually displayed

2. Determine where an 800 x 800 image is that overflows the display frame buffer.

pl> display image800 1
pl> imdisp_pos
pl> lpar imdisp_pos
image = "image800"    Displayed image specification
(left = 0.)             Left side of viewport, NDC
(right = 1.)             Right side of viewport, NDC
(bottom = 0.)             Bottom side of viewport, NDC
(top = 1.)             Top side of viewport, NDC
(section = "image800[145:656,145:656]") Section actually displayed

3. Determine where an 800 x 800 image is diplayed within a square that is 80% of the display size.

pl> display image800 fill+ xsize=.8 ysize=.8
pl> imdisp_pos
pl> lpar imdisp_pos
image = "image800"    Displayed image specification
(left = 0.1001251488924) Left side of viewport, NDC
(right = 0.90012508630753) Right side of viewport, NDC
(bottom = 0.099874846637249) Bottom side of viewport, NDC
(top = 0.89987480640412) Top side of viewport, NDC
(section = "image800[1:800,1:800]") Section actually displayed

BUGS

This task uses a "restricted interface" to the image display. If the image display interface ever changes, this will meet a horrible and untimely death. However, if a change does occur, it will be to incorporate both graphics and image display into a nice, neat package, and this task will no longer be needed.

Another bug relates to the fact that graphics and image display are not integrated. Graphics overlays onto the image display suffer from various roundoff errors. Only setting the parameter display.fill=no will produce a reasonable match between graphics and image display.

SEE ALSO

display, imdkern