Palette Premultiplication Consistency Check
Check necessary byte-range consistency for purported premultiplied RGB channels not exceeding alpha; passing does not prove correct premultiplication.
Description
Check necessary byte-range consistency for purported premultiplied RGB channels not exceeding alpha; passing does not prove correct premultiplication.
In a normalized premultiplied-byte representation, color channels cannot exceed alpha. Violating that bound is a useful partial screen.
When to use this tool
Check necessary byte-range consistency for purported premultiplied RGB channels not exceeding alpha; passing does not prove correct premultiplication.
- Prepare the supplied paletteJson 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 paletteJson. 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.violations. Interpret false, null and empty lists using the distinctions below; they can be valid outputs.
Parse byte RGBA records and report each entry whose red, green or blue byte exceeds its alpha byte.1
| Input field | Meaning and representation | Accepted input |
|---|---|---|
| paletteJson | JSON text, entered as one text field. The decoded structure is illustrated below; it is not a separate file. | Text |
For the JSON text fields, the following decoded structures show the example records before they are serialized into input strings. Keep field names, list nesting and value types as shown.
[
{
"field": "paletteJson",
"decoded": [
{
"id": "a",
"name": "Red",
"rgba": [
255,
0,
0,
255
]
},
{
"id": "b",
"name": "red",
"rgba": [
255,
0,
0,
0
]
}
]
}
]| Output field | Interpretation |
|---|---|
| result | Object containing the named outputs below. |
| result.violations | Source positions or records that fail the specific screen above; an empty list means no such violation. |
{
"input": {
"paletteJson": "[{\"id\":\"a\",\"name\":\"Red\",\"rgba\":[255,0,0,255]},{\"id\":\"b\",\"name\":\"red\",\"rgba\":[255,0,0,0]}]"
},
"output": {
"result": {
"violations": [
{
"index": 1,
"id": "b"
}
]
}
}
}Limitations and assumptions
- Passing this necessary bound does not prove correct premultiplication or compositing. Straight-alpha colors can legitimately fail it; no conversion is performed.
- Palette records contain string id/name and exactly four RGBA bytes from zero through 255; at most 128 records are accepted. Duplicate IDs or names remain allowed unless this operation explicitly audits or rejects them.
- 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.
- Lists are limited to 128 entries. JSON text must meet bounded size and depth checks, and numeric outputs beyond the safe finite magnitude are rejected. Exact large integers use decimal strings.
- 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
Use actual rendering or a color-managed workflow when comparing perceived color and transparency. Index changes need corresponding updates to their consumers; name and role checks do not establish visual accessibility.
References
Similar or alternative tools
- Palette Adjacent Repeat Audit
Audit adjacent exact RGBA palette repeats, excluding RGB-only matches whose alpha differs; caller ordering is preserved.
- Palette Alpha Presence Summary
Count transparent, opaque and partially transparent RGBA palette byte entries; no compositing or color-space conversion.