SkColorTable.h

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/*
 * Copyright 2023 Google LLC
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */
 
#ifndef SkColorTable_DEFINED
#define SkColorTable_DEFINED
 
#include "include/core/SkBitmap.h"
#include "include/core/SkRefCnt.h"
#include "include/private/base/SkAPI.h"
 
#include <cstdint>
 
class SkReadBuffer;
class SkWriteBuffer;
 
/**
 * SkColorTable holds the lookup tables for each channel (ARGB) used to define the filter behavior
 * of `SkColorFilters::Table`, and provides a way to share the table data between client code and
 * the returned SkColorFilter. Once created, an SkColorTable is immutable.
*/
class SK_API SkColorTable : public SkRefCnt {
public:
    // Creates a new SkColorTable with 'table' used for all four channels. The table is copied into
    // the SkColorTable.
    static sk_sp<SkColorTable> Make(const uint8_t table[256]) {
        return Make(table, table, table, table);
    }
 
    // Creates a new SkColorTable with the per-channel lookup tables. Each non-null table is copied
    // into the SkColorTable. Null parameters are interpreted as the identity table.
    static sk_sp<SkColorTable> Make(const uint8_t tableA[256],
                                    const uint8_t tableR[256],
                                    const uint8_t tableG[256],
                                    const uint8_t tableB[256]);
 
    // Per-channel constant value lookup (0-255).
    const uint8_t* alphaTable() const { return fTable.getAddr8(0, 0); }
    const uint8_t* redTable()   const { return fTable.getAddr8(0, 1); }
    const uint8_t* greenTable() const { return fTable.getAddr8(0, 2); }
    const uint8_t* blueTable()  const { return fTable.getAddr8(0, 3); }
 
    void flatten(SkWriteBuffer& buffer) const;
 
    static sk_sp<SkColorTable> Deserialize(SkReadBuffer& buffer);
 
private:
    friend class SkTableColorFilter; // for bitmap()
 
    SkColorTable(const SkBitmap& table) : fTable(table) {}
 
    // The returned SkBitmap is immutable; attempting to modify its pixel data will trigger asserts
    // in debug builds and cause undefined behavior in release builds.
    const SkBitmap& bitmap() const { return fTable; }
 
    SkBitmap fTable; // A 256x4 A8 image
};
 
#endif // SkColorTable_DEFINED