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      1 /*
      2  * Copyright (C) 2013 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 #ifndef ANDROID_HWUI_UV_MAPPER_H
     18 #define ANDROID_HWUI_UV_MAPPER_H
     19 
     20 #include "Rect.h"
     21 
     22 namespace android {
     23 namespace uirenderer {
     24 
     25 /**
     26  * This class can be used to map UV coordinates from the [0..1]
     27  * range to other arbitrary ranges. All the methods below assume
     28  * that the input values lie in the [0..1] range already.
     29  */
     30 class UvMapper {
     31 public:
     32     /**
     33      * Using this constructor is equivalent to not using any mapping at all.
     34      * UV coordinates in the [0..1] range remain in the [0..1] range.
     35      */
     36     UvMapper(): mIdentity(true), mMinU(0.0f), mMaxU(1.0f), mMinV(0.0f), mMaxV(1.0f) {
     37     }
     38 
     39     /**
     40      * Creates a new mapper with the specified ranges for U and V coordinates.
     41      * The parameter minU must be < maxU and minV must be < maxV.
     42      */
     43     UvMapper(float minU, float maxU, float minV, float maxV):
     44         mMinU(minU), mMaxU(maxU), mMinV(minV), mMaxV(maxV) {
     45         checkIdentity();
     46     }
     47 
     48     /**
     49      * Returns true if calling the map*() methods has no effect (that is,
     50      * texture coordinates remain in the 0..1 range.)
     51      */
     52     bool isIdentity() const {
     53         return mIdentity;
     54     }
     55 
     56     /**
     57      * Changes the U and V mapping ranges.
     58      * The parameter minU must be < maxU and minV must be < maxV.
     59      */
     60     void setMapping(float minU, float maxU, float minV, float maxV) {
     61         mMinU = minU;
     62         mMaxU = maxU;
     63         mMinV = minV;
     64         mMaxV = maxV;
     65         checkIdentity();
     66     }
     67 
     68     /**
     69      * Maps a single value in the U range.
     70      */
     71     void mapU(float& u) const {
     72         if (!mIdentity) u = lerp(mMinU, mMaxU, u);
     73     }
     74 
     75     /**
     76      * Maps a single value in the V range.
     77      */
     78     void mapV(float& v) const {
     79         if (!mIdentity) v = lerp(mMinV, mMaxV, v);
     80     }
     81 
     82     /**
     83      * Maps the specified rectangle in place. This method assumes:
     84      * - left = min. U
     85      * - top = min. V
     86      * - right = max. U
     87      * - bottom = max. V
     88      */
     89     void map(Rect& texCoords) const {
     90         if (!mIdentity) {
     91             texCoords.left = lerp(mMinU, mMaxU, texCoords.left);
     92             texCoords.right = lerp(mMinU, mMaxU, texCoords.right);
     93             texCoords.top = lerp(mMinV, mMaxV, texCoords.top);
     94             texCoords.bottom = lerp(mMinV, mMaxV, texCoords.bottom);
     95         }
     96     }
     97 
     98     /**
     99      * Maps the specified UV coordinates in place.
    100      */
    101     void map(float& u1, float& v1, float& u2, float& v2) const {
    102         if (!mIdentity) {
    103             u1 = lerp(mMinU, mMaxU, u1);
    104             u2 = lerp(mMinU, mMaxU, u2);
    105             v1 = lerp(mMinV, mMaxV, v1);
    106             v2 = lerp(mMinV, mMaxV, v2);
    107         }
    108     }
    109 
    110     void dump() const {
    111         ALOGD("mapper[minU=%.2f maxU=%.2f minV=%.2f maxV=%.2f]", mMinU, mMaxU, mMinV, mMaxV);
    112     }
    113 
    114 private:
    115     static float lerp(float start, float stop, float amount) {
    116         return start + (stop - start) * amount;
    117     }
    118 
    119     void checkIdentity() {
    120         mIdentity = mMinU == 0.0f && mMaxU == 1.0f && mMinV == 0.0f && mMaxV == 1.0f;
    121     }
    122 
    123     bool mIdentity;
    124     float mMinU;
    125     float mMaxU;
    126     float mMinV;
    127     float mMaxV;
    128 };
    129 
    130 }; // namespace uirenderer
    131 }; // namespace android
    132 
    133 #endif // ANDROID_HWUI_UV_MAPPER_H
    134