TransferParameters.kt
/*
* Copyright 2019 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package androidx.compose.ui.graphics.colorspace
/**
* Defines the parameters for the ICC parametric curve type 4, as
* defined in ICC.1:2004-10, section 10.15.
*
* [The EOTF is of the form linked here](https://d.android.com/reference/android/graphics/ColorSpace.Rgb.TransferParameters)
*
* The corresponding OETF is simply the inverse function.
*
* The parameters defined by this class form a valid transfer
* function only if all the following conditions are met:
*
* * No parameter is a [Not-a-Number][Double.isNaN]
* * `d` is in the range `[0..1]`
* * The function is not constant
* * The function is positive and increasing
*/
data class TransferParameters(
/** Value g in the equation of the EOTF described above. */
val gamma: Double,
/** Value a in the equation of the EOTF described above. */
val a: Double,
/** Value b in the equation of the EOTF described above. */
val b: Double,
/** Value c in the equation of the EOTF described above. */
val c: Double,
/** Value d in the equation of the EOTF described above. */
val d: Double,
/** Value e in the equation of the EOTF described above. */
val e: Double = 0.0,
/** Value f in the equation of the EOTF described above. */
val f: Double = 0.0
) {
init {
if (a.isNaN() || b.isNaN() || c.isNaN() || d.isNaN() || e.isNaN() || f.isNaN() ||
gamma.isNaN()
) {
throw IllegalArgumentException("Parameters cannot be NaN")
}
// Next representable float after 1.0
// We use doubles here but the representation inside our native code is often floats
if (!(d >= 0.0 && d <= 1.0)) {
throw IllegalArgumentException(
"Parameter d must be in the range [0..1], was " +
"$d"
)
}
if (d == 0.0 && (a == 0.0 || gamma == 0.0)) {
throw IllegalArgumentException(
"Parameter a or g is zero, the transfer function is constant"
)
}
if (d >= 1.0 && c == 0.0) {
throw IllegalArgumentException(
"Parameter c is zero, the transfer function is constant"
)
}
if ((a == 0.0 || gamma == 0.0) && c == 0.0) {
throw IllegalArgumentException(
"Parameter a or g is zero," +
" and c is zero, the transfer function is constant"
)
}
if (c < 0.0) {
throw IllegalArgumentException("The transfer function must be increasing")
}
if (a < 0.0 || gamma < 0.0) {
throw IllegalArgumentException(
(
"The transfer function must be " +
"positive or increasing"
)
)
}
}
}