include/encode/SkPngEncoder.h

/*
 * Copyright 2017 Google LLC
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#ifndef SkPngEncoder_DEFINED
#define SkPngEncoder_DEFINED

#include "include/core/SkDataTable.h"
#include "include/core/SkRefCnt.h"
#include "include/private/SkAPI.h"
#include "include/private/SkHdrMetadata.h"

// TODO(kjlubick) update clients to directly include this
#include "include/encode/SkEncoder.h"  // IWYU pragma: keep

#include <memory>

class GrDirectContext;
class SkData;
class SkImage;
class SkPixmap;
class SkWStream;
struct skcms_ICCProfile;
struct SkGainmapInfo;

namespace SkPngEncoder {

enum class FilterFlag : int {
    kZero = 0x00,
    kNone = 0x08,
    kSub = 0x10,
    kUp = 0x20,
    kAvg = 0x40,
    kPaeth = 0x80,
    kAll = kNone | kSub | kUp | kAvg | kPaeth,
};

inline FilterFlag operator|(FilterFlag x, FilterFlag y) { return (FilterFlag)((int)x | (int)y); }

struct Options {
    /**
     *  Selects which filtering strategies to use.
     *
     *  If a single filter is chosen, libpng will use that filter for every row.
     *
     *  If multiple filters are chosen, libpng will use a heuristic to guess which filter
     *  will encode smallest, then apply that filter.  This happens on a per row basis,
     *  different rows can use different filters.
     *
     *  Using a single filter (or less filters) is typically faster.  Trying all of the
     *  filters may help minimize the output file size.
     *
     *  Our default value matches libpng's default.
     */
    FilterFlag fFilterFlags = FilterFlag::kAll;

    /**
     *  Must be in [0, 9] where 9 corresponds to maximal compression.  This value is passed
     *  directly to zlib.  0 is a special case to skip zlib entirely, creating dramatically
     *  larger pngs.
     *
     *  Our default value matches libpng's default.
     */
    int fZLibLevel = 6;

    /**
     *  Represents comments in the tEXt ancillary chunk of the png.
     *  The 2i-th entry is the keyword for the i-th comment,
     *  and the (2i + 1)-th entry is the text for the i-th comment.
     */
    sk_sp<SkDataTable> fComments;

    /**
     * Container for any HDR metadata to include in the encoded image.
     */
    skhdr::Metadata fHdrMetadata;

    /**
     * If non-null, then a gainmap and its metadata will be encoded as png chunks.
     * The gainmap will be encoded in a gmAP chunk as a full PNG container. The
     * gainmap info will be encoded in a gdAT chunk inside of the gmAP chunk.
     * This effectively is Option B proposed in this discussion for adding gainmaps
     * into PNG: https://github.com/w3c/png/issues/380#issuecomment-2325163149.
     *
     * Note that if fGainmapInfo is null, then fGainmap will fail to encode, as the
     * gainmap metadata is required to correctly interpret the encoded gainmap.
     */
    const SkPixmap* fGainmap = nullptr;
    const SkGainmapInfo* fGainmapInfo = nullptr;
};

/**
 *  Encode the |src| pixels to the |dst| stream.
 *  |options| may be used to control the encoding behavior.
 *
 *  Returns true on success.  Returns false on an invalid or unsupported |src|.
 */
SK_API bool Encode(SkWStream* dst, const SkPixmap& src, const Options& options);

/**
 *  Returns the encoded data for the pixmap, or nullptr on failure.
 */
SK_API sk_sp<SkData> Encode(const SkPixmap& src, const Options& options);

/**
*  Encode the provided image and return the resulting bytes. If the image was created as
*  a texture-backed image on a GPU context, that |ctx| must be provided so the pixels
*  can be read before being encoded. For raster-backed images, |ctx| can be nullptr.
*  |options| may be used to control the encoding behavior.
*
*  Returns nullptr if the pixels could not be read or encoding otherwise fails.
*/
SK_API sk_sp<SkData> Encode(GrDirectContext* ctx, const SkImage* img, const Options& options);

/**
 *  Create a png encoder that will encode the |src| pixels to the |dst| stream.
 *  |options| may be used to control the encoding behavior.
 *
 *  The primary use of this is incremental encoding of the pixels.
 *
 *  |dst| is unowned but must remain valid for the lifetime of the object.
 *
 *  This returns nullptr on an invalid or unsupported |src|.
 */
SK_API std::unique_ptr<SkEncoder> Make(SkWStream* dst, const SkPixmap& src, const Options& options);

}  // namespace SkPngEncoder

#endif