Rectangle Visibility Fraction
Compute geometric visible area fraction of a positive-area rectangle; clipping, transforms, occlusion and opacity are not modeled.
Description
Compute geometric visible area fraction of a positive-area rectangle; clipping, transforms, occlusion and opacity are not modeled.
Visible area fraction compares one rectangle with its viewport intersection, independent of other occluding content.
When to use this tool
Compute geometric visible area fraction of a positive-area rectangle; clipping, transforms, occlusion and opacity are not modeled.
- Prepare the supplied rectangle, viewport fields for this operation.
- Compare the complete example with the representation used by your own input before carrying the result into another step.
How to use the tool and how it works
- Enter rectangle, viewport. Use the exact text syntax, units and index conventions explained below.
- Run the tool. If input validation fails, correct the supplied fields before interpreting any result.
- Read result.visibleArea, result.visibleFraction. Interpret false, null and empty lists using the distinctions below; they can be valid outputs.
Require a positive item area. Intersect the two origin/extent rectangles and return overlap area plus that area divided by the item's full area.1
| Input field | Meaning and representation | Accepted input |
|---|---|---|
| rectangle | rectangle. | List of finite numbers; bounded by the operation; greater than zero |
| viewport | viewport. | List of finite numbers; bounded by the operation |
| Output field | Interpretation |
|---|---|
| result | Object containing the named outputs below. |
| result.visibleArea | The visible area value under the stated formula or text convention. |
| result.visibleFraction | Visible intersection area divided by item area; a fraction from zero through one. |
{
"input": {
"rectangle": [
0,
0,
10,
10
],
"viewport": [
5,
0,
10,
10
]
},
"output": {
"result": {
"visibleArea": 50,
"visibleFraction": 0.5
}
}
}Limitations and assumptions
- The fraction lies on a zero-to-one scale. Z-order, clipping ancestors, transparency and actual on-screen visibility are not checked.
- Rectangle arrays use [x,y,width,height] with nonnegative extents. All dimensions must use the same coordinate frame and unit; values are supplied rather than measured from a page.
- Every declared top-level field is required and unexpected fields are rejected. Numeric inputs must be finite; ordinary text fields are bounded to 8,192 UTF-16 code units, with tighter operation-specific limits where stated.
- String lists have at most 128 entries of at most 128 code units; matrices have at most 128 rows and columns. Larger numeric lists and parsed JSON have separate bounded budgets. Nonfinite results and excessively large serialized outputs are rejected.
- Indexes are zero-based and spans have an exclusive end unless explicitly stated otherwise. A valid false, null or empty-list result is distinct from malformed input.
Alternative or Complementary methods
Measure the actual layout when browser behavior matters. The formulas use supplied coordinates and explicit simplifications; they do not account for every box, writing mode, clipping ancestor or simultaneous layout change.
References
Similar or alternative tools
- Layout Inset Content Rectangle
Compute axis-aligned inset content geometry, retaining an overconstrained flag when opposing insets exceed available size.
- Layout Rectangle Overlap Pairs
List unique unordered rectangle pairs with positive overlap area; edge touching, z-order and occlusion are not counted as area overlap.