src/codec/SkPngCodecBase.h

/*
 * Copyright 2024 Google LLC
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */
#ifndef SkPngCodecBase_DEFINED
#define SkPngCodecBase_DEFINED

#include <cstddef>
#include <cstdint>
#include <memory>
#include <optional>

#include "include/codec/SkCodec.h"
#include "include/codec/SkEncodedOrigin.h"
#include "include/core/SkImageInfo.h"
#include "include/core/SkRefCnt.h"
#include "include/core/SkSpan.h"
#include "include/private/SkDebug.h"
#include "include/private/SkEncodedInfo.h"
#include "include/private/SkGainmapInfo.h"
#include "src/codec/SkCodecPriv.h"
#include "src/codec/SkPngCompositeChunkReader.h"

class SkColorPalette;
class SkSampler;
class SkStream;
class SkSwizzler;
enum class SkEncodedImageFormat;

// This class implements functionality shared between `SkPngCodec` and
// `SkPngRustCodec`.
class SkPngCodecBase : public SkCodec {
public:
    ~SkPngCodecBase() override;

    static bool IsPng(const void*, size_t);

    static bool isCompatibleColorProfileAndType(const SkCodecs::ColorProfile* profile,
                                                SkEncodedInfo::Color color);
protected:
    SkPngCodecBase(SkEncodedInfo&&,
                   std::unique_ptr<SkStream>,
                   SkEncodedOrigin origin,
                   sk_sp<SkPngCompositeChunkReader> chunkReader,
                   std::unique_ptr<SkStream> gainmapStream,
                   std::optional<SkGainmapInfo> gainmapInfo);

    // Initialize most fields needed by `applyXformRow`.
    //
    // Each call to `applyXformRow` will transform `frameWidth` pixels
    // (which may be less than `dstInfo.width()` when decoding frames that
    // depend on earlier frames).
    Result initializeXforms(const SkImageInfo& dstInfo, const Options& options, int frameWidth);

    // Initialize other fields needed by `applyXformRow`.
    //
    // Needs to be called *after* (i.e. outside of) `onStartIncrementalDecode`.
    // This timing ensures that the `swizzler` (if present) is in its final
    // state (e.g. setting up subsampling by the user of the codec can affect `swizzleWidth`).
    void initializeXformParams();

    // Transforms a decoded row into the `dstInfo` format that was earlier
    // passed to `initializeXforms`.
    //
    // The first bytes/pixels of `srcRow` will be transformed into the first
    // bytes/pixels of `dstRow`.  In other words, the transformation ignores
    // `fcTL.x_offset` field - the caller should offset `dstRow` if desired
    // (it may not be desirable when working with interlaced rows which are
    // first transformed into an intermediate buffer).
    void applyXformRow(SkSpan<uint8_t> dstRow, SkSpan<const uint8_t> srcRow);
    void applyXformRow(void* dstRow, const uint8_t* srcRow);

    size_t getEncodedRowBytes() const { return fEncodedRowBytes; }
    size_t getDstRowSize() const { return fDstRowSize; }
    const SkSwizzler* swizzler() const { return fSwizzler.get(); }

    struct PaletteColorEntry {
        uint8_t red;
        uint8_t green;
        uint8_t blue;
    };
    virtual std::optional<SkSpan<const PaletteColorEntry>> onTryGetPlteChunk() = 0;
    virtual std::optional<SkSpan<const uint8_t>> onTryGetTrnsChunk() = 0;

    virtual std::unique_ptr<SkCodec> onDecodeGainmap(std::unique_ptr<SkStream> stream,
                                                     SkCodec::Result* result) = 0;

    sk_sp<SkPngCompositeChunkReader> fPngChunkReader;

    // SkCodec overrides:
    SkSampler* getSampler(bool createIfNecessary) override;

private:
    bool onGetGainmapCodec(SkGainmapInfo* info, std::unique_ptr<SkCodec>* gainmapCodec) final;
    bool onGetGainmapInfo(SkGainmapInfo* info) final;

    // SkCodec overrides:
    SkEncodedImageFormat onGetEncodedFormat() const final;

    Result allocateStorage(const SkImageInfo& dstInfo);
    Result initializeSwizzler(const SkImageInfo& dstInfo,
                              const Options& options,
                              bool skipFormatConversion,
                              int frameWidth);
    bool createColorTable(const SkImageInfo& dstInfo);

    enum XformMode {
        // Requires only a swizzle pass.
        kSwizzleOnly_XformMode,

        // Requires only a color xform pass.
        kColorOnly_XformMode,

        // Requires a swizzle and a color xform.
        kSwizzleColor_XformMode,
    };
    XformMode fXformMode;

    std::unique_ptr<SkSwizzler> fSwizzler;
    SkCodecPriv::BudgetedBuffer fStorage;
    int fXformWidth = -1;
    sk_sp<SkColorPalette> fColorTable;

    size_t fEncodedRowBytes = 0;  // Size of encoded/source row in bytes.
    size_t fDstRowSize = 0;       // Size of active destination row in bytes (excluding padding).

    std::optional<SkImageInfo> fDstInfoOfPreviousColorTableCreation;

    std::unique_ptr<SkStream> fGainmapStream;
    std::optional<SkGainmapInfo> fGainmapInfo;
};

#endif  // SkPngCodecBase_DEFINED