Carla/source/modules/juce_graphics/image_formats/juce_PNGLoader.cpp

/*
  ==============================================================================

   This file is part of the JUCE 6 technical preview.
   Copyright (c) 2020 - Raw Material Software Limited

   You may use this code under the terms of the GPL v3
   (see www.gnu.org/licenses).

   For this technical preview, this file is not subject to commercial licensing.

   JUCE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL WARRANTIES, WHETHER
   EXPRESSED OR IMPLIED, INCLUDING MERCHANTABILITY AND FITNESS FOR PURPOSE, ARE
   DISCLAIMED.

  ==============================================================================
*/

namespace juce
{

JUCE_BEGIN_IGNORE_WARNINGS_MSVC (4390 4611 4365 4267 4616 2544 2545)

namespace zlibNamespace
{
#if JUCE_INCLUDE_ZLIB_CODE
  #undef OS_CODE
  #undef fdopen
  #define ZLIB_INTERNAL
  #define NO_DUMMY_DECL
  #include <juce_core/zip/zlib/zlib.h>
  #undef OS_CODE
#else
  #include JUCE_ZLIB_INCLUDE_PATH
#endif
}

#if ! defined (jmp_buf) || ! defined (longjmp)
 #include <setjmp.h>
#endif

namespace pnglibNamespace
{
  using namespace zlibNamespace;

#if JUCE_INCLUDE_PNGLIB_CODE || ! defined (JUCE_INCLUDE_PNGLIB_CODE)

  #if _MSC_VER != 1310
   using std::calloc; // (causes conflict in VS.NET 2003)
   using std::malloc;
   using std::free;
  #endif

   JUCE_BEGIN_IGNORE_WARNINGS_GCC_LIKE ("-Wsign-conversion",
                                        "-Wimplicit-fallthrough",
                                        "-Wtautological-constant-out-of-range-compare",
                                        "-Wzero-as-null-pointer-constant",
                                        "-Wcomma")

  #undef check
  using std::abs;
  #define NO_DUMMY_DECL
  #define PNGLCONF_H 1

 #if JUCE_ANDROID
  #define PNG_ARM_NEON_SUPPORTED
 #endif

  #define PNG_16BIT_SUPPORTED
  #define PNG_ALIGNED_MEMORY_SUPPORTED
  #define PNG_BENIGN_ERRORS_SUPPORTED
  #define PNG_BENIGN_READ_ERRORS_SUPPORTED
  #define PNG_CHECK_FOR_INVALID_INDEX_SUPPORTED
  #define PNG_COLORSPACE_SUPPORTED
  #define PNG_CONSOLE_IO_SUPPORTED
  #define PNG_EASY_ACCESS_SUPPORTED
  #define PNG_FIXED_POINT_SUPPORTED
  #define PNG_FLOATING_ARITHMETIC_SUPPORTED
  #define PNG_FLOATING_POINT_SUPPORTED
  #define PNG_FORMAT_AFIRST_SUPPORTED
  #define PNG_FORMAT_BGR_SUPPORTED
  #define PNG_GAMMA_SUPPORTED
  #define PNG_GET_PALETTE_MAX_SUPPORTED
  #define PNG_HANDLE_AS_UNKNOWN_SUPPORTED
  #define PNG_INCH_CONVERSIONS_SUPPORTED
  #define PNG_INFO_IMAGE_SUPPORTED
  #define PNG_IO_STATE_SUPPORTED
  #define PNG_POINTER_INDEXING_SUPPORTED
  #define PNG_PROGRESSIVE_READ_SUPPORTED
  #define PNG_READ_16BIT_SUPPORTED
  #define PNG_READ_ALPHA_MODE_SUPPORTED
  #define PNG_READ_ANCILLARY_CHUNKS_SUPPORTED
  #define PNG_READ_BACKGROUND_SUPPORTED
  #define PNG_READ_BGR_SUPPORTED
  #define PNG_READ_CHECK_FOR_INVALID_INDEX_SUPPORTED
  #define PNG_READ_COMPOSITE_NODIV_SUPPORTED
  #define PNG_READ_COMPRESSED_TEXT_SUPPORTED
  #define PNG_READ_EXPAND_16_SUPPORTED
  #define PNG_READ_EXPAND_SUPPORTED
  #define PNG_READ_FILLER_SUPPORTED
  #define PNG_READ_GAMMA_SUPPORTED
  #define PNG_READ_GET_PALETTE_MAX_SUPPORTED
  #define PNG_READ_GRAY_TO_RGB_SUPPORTED
  #define PNG_READ_INTERLACING_SUPPORTED
  #define PNG_READ_INT_FUNCTIONS_SUPPORTED
  #define PNG_READ_INVERT_ALPHA_SUPPORTED
  #define PNG_READ_INVERT_SUPPORTED
  #define PNG_READ_OPT_PLTE_SUPPORTED
  #define PNG_READ_PACKSWAP_SUPPORTED
  #define PNG_READ_PACK_SUPPORTED
  #define PNG_READ_QUANTIZE_SUPPORTED
  #define PNG_READ_RGB_TO_GRAY_SUPPORTED
  #define PNG_READ_SCALE_16_TO_8_SUPPORTED
  #define PNG_READ_SHIFT_SUPPORTED
  #define PNG_READ_STRIP_16_TO_8_SUPPORTED
  #define PNG_READ_STRIP_ALPHA_SUPPORTED
  #define PNG_READ_SUPPORTED
  #define PNG_READ_SWAP_ALPHA_SUPPORTED
  #define PNG_READ_SWAP_SUPPORTED
  #define PNG_READ_TEXT_SUPPORTED
  #define PNG_READ_TRANSFORMS_SUPPORTED
  #define PNG_READ_UNKNOWN_CHUNKS_SUPPORTED
  #define PNG_READ_USER_CHUNKS_SUPPORTED
  #define PNG_READ_USER_TRANSFORM_SUPPORTED
  #define PNG_READ_bKGD_SUPPORTED
  #define PNG_READ_cHRM_SUPPORTED
  #define PNG_READ_gAMA_SUPPORTED
  #define PNG_READ_hIST_SUPPORTED
  #define PNG_READ_iCCP_SUPPORTED
  #define PNG_READ_iTXt_SUPPORTED
  #define PNG_READ_oFFs_SUPPORTED
  #define PNG_READ_pCAL_SUPPORTED
  #define PNG_READ_pHYs_SUPPORTED
  #define PNG_READ_sBIT_SUPPORTED
  #define PNG_READ_sCAL_SUPPORTED
  #define PNG_READ_sPLT_SUPPORTED
  #define PNG_READ_sRGB_SUPPORTED
  #define PNG_READ_tEXt_SUPPORTED
  #define PNG_READ_tIME_SUPPORTED
  #define PNG_READ_tRNS_SUPPORTED
  #define PNG_READ_zTXt_SUPPORTED
  #define PNG_SAVE_INT_32_SUPPORTED
  #define PNG_SAVE_UNKNOWN_CHUNKS_SUPPORTED
  #define PNG_SEQUENTIAL_READ_SUPPORTED
  #define PNG_SET_CHUNK_CACHE_LIMIT_SUPPORTED
  #define PNG_SET_CHUNK_MALLOC_LIMIT_SUPPORTED
  #define PNG_SET_UNKNOWN_CHUNKS_SUPPORTED
  #define PNG_SET_USER_LIMITS_SUPPORTED
  #define PNG_SIMPLIFIED_READ_AFIRST_SUPPORTED
  #define PNG_SIMPLIFIED_READ_BGR_SUPPORTED
  #define PNG_SIMPLIFIED_WRITE_AFIRST_SUPPORTED
  #define PNG_SIMPLIFIED_WRITE_BGR_SUPPORTED
  #define PNG_STDIO_SUPPORTED
  #define PNG_STORE_UNKNOWN_CHUNKS_SUPPORTED
  #define PNG_TEXT_SUPPORTED
  #define PNG_TIME_RFC1123_SUPPORTED
  #define PNG_UNKNOWN_CHUNKS_SUPPORTED
  #define PNG_USER_CHUNKS_SUPPORTED
  #define PNG_USER_LIMITS_SUPPORTED
  #define PNG_USER_TRANSFORM_INFO_SUPPORTED
  #define PNG_USER_TRANSFORM_PTR_SUPPORTED
  #define PNG_WARNINGS_SUPPORTED
  #define PNG_WRITE_16BIT_SUPPORTED
  #define PNG_WRITE_ANCILLARY_CHUNKS_SUPPORTED
  #define PNG_WRITE_BGR_SUPPORTED
  #define PNG_WRITE_CHECK_FOR_INVALID_INDEX_SUPPORTED
  #define PNG_WRITE_COMPRESSED_TEXT_SUPPORTED
  #define PNG_WRITE_CUSTOMIZE_ZTXT_COMPRESSION_SUPPORTED
  #define PNG_WRITE_FILLER_SUPPORTED
  #define PNG_WRITE_FILTER_SUPPORTED
  #define PNG_WRITE_FLUSH_SUPPORTED
  #define PNG_WRITE_GET_PALETTE_MAX_SUPPORTED
  #define PNG_WRITE_INTERLACING_SUPPORTED
  #define PNG_WRITE_INT_FUNCTIONS_SUPPORTED
  #define PNG_WRITE_INVERT_ALPHA_SUPPORTED
  #define PNG_WRITE_INVERT_SUPPORTED
  #define PNG_WRITE_OPTIMIZE_CMF_SUPPORTED
  #define PNG_WRITE_PACKSWAP_SUPPORTED
  #define PNG_WRITE_PACK_SUPPORTED
  #define PNG_WRITE_SHIFT_SUPPORTED
  #define PNG_WRITE_SUPPORTED
  #define PNG_WRITE_SWAP_ALPHA_SUPPORTED
  #define PNG_WRITE_SWAP_SUPPORTED
  #define PNG_WRITE_TEXT_SUPPORTED
  #define PNG_WRITE_TRANSFORMS_SUPPORTED
  #define PNG_WRITE_UNKNOWN_CHUNKS_SUPPORTED
  #define PNG_WRITE_USER_TRANSFORM_SUPPORTED
  #define PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
  #define PNG_WRITE_bKGD_SUPPORTED
  #define PNG_WRITE_cHRM_SUPPORTED
  #define PNG_WRITE_gAMA_SUPPORTED
  #define PNG_WRITE_hIST_SUPPORTED
  #define PNG_WRITE_iCCP_SUPPORTED
  #define PNG_WRITE_iTXt_SUPPORTED
  #define PNG_WRITE_oFFs_SUPPORTED
  #define PNG_WRITE_pCAL_SUPPORTED
  #define PNG_WRITE_pHYs_SUPPORTED
  #define PNG_WRITE_sBIT_SUPPORTED
  #define PNG_WRITE_sCAL_SUPPORTED
  #define PNG_WRITE_sPLT_SUPPORTED
  #define PNG_WRITE_sRGB_SUPPORTED
  #define PNG_WRITE_tEXt_SUPPORTED
  #define PNG_WRITE_tIME_SUPPORTED
  #define PNG_WRITE_tRNS_SUPPORTED
  #define PNG_WRITE_zTXt_SUPPORTED
  #define PNG_bKGD_SUPPORTED
  #define PNG_cHRM_SUPPORTED
  #define PNG_gAMA_SUPPORTED
  #define PNG_hIST_SUPPORTED
  #define PNG_iCCP_SUPPORTED
  #define PNG_iTXt_SUPPORTED
  #define PNG_oFFs_SUPPORTED
  #define PNG_pCAL_SUPPORTED
  #define PNG_pHYs_SUPPORTED
  #define PNG_sBIT_SUPPORTED
  #define PNG_sCAL_SUPPORTED
  #define PNG_sPLT_SUPPORTED
  #define PNG_sRGB_SUPPORTED
  #define PNG_tEXt_SUPPORTED
  #define PNG_tIME_SUPPORTED
  #define PNG_tRNS_SUPPORTED
  #define PNG_zTXt_SUPPORTED

  #define PNG_STRING_COPYRIGHT "";
  #define PNG_STRING_NEWLINE "\n"
  #define PNG_LITERAL_SHARP 0x23
  #define PNG_LITERAL_LEFT_SQUARE_BRACKET 0x5b
  #define PNG_LITERAL_RIGHT_SQUARE_BRACKET 0x5d

  #define PNG_API_RULE 0
  #define PNG_CALLOC_SUPPORTED
  #define PNG_COST_SHIFT 3
  #define PNG_DEFAULT_READ_MACROS 1
  #define PNG_GAMMA_THRESHOLD_FIXED 5000
  #define PNG_IDAT_READ_SIZE PNG_ZBUF_SIZE
  #define PNG_INFLATE_BUF_SIZE 1024
  #define PNG_MAX_GAMMA_8 11
  #define PNG_QUANTIZE_BLUE_BITS 5
  #define PNG_QUANTIZE_GREEN_BITS 5
  #define PNG_QUANTIZE_RED_BITS 5
  #define PNG_TEXT_Z_DEFAULT_COMPRESSION (-1)
  #define PNG_TEXT_Z_DEFAULT_STRATEGY 0
  #define PNG_WEIGHT_SHIFT 8
  #define PNG_ZBUF_SIZE 8192
  #define PNG_Z_DEFAULT_COMPRESSION (-1)
  #define PNG_Z_DEFAULT_NOFILTER_STRATEGY 0
  #define PNG_Z_DEFAULT_STRATEGY 1
  #define PNG_sCAL_PRECISION 5
  #define PNG_sRGB_PROFILE_CHECKS 2

  #define PNG_LINKAGE_API
  #define PNG_LINKAGE_FUNCTION

  #define PNG_ARM_NEON_OPT 0

  #if ! defined (PNG_USER_WIDTH_MAX)
   #define PNG_USER_WIDTH_MAX 1000000
  #endif

  #if ! defined (PNG_USER_HEIGHT_MAX)
   #define PNG_USER_HEIGHT_MAX 1000000
  #endif

  #define png_debug(a, b)
  #define png_debug1(a, b, c)
  #define png_debug2(a, b, c, d)

  #include "pnglib/png.h"
  #include "pnglib/pngconf.h"

  #define PNG_NO_EXTERN
  #include "pnglib/png.c"
  #include "pnglib/pngerror.c"
  #include "pnglib/pngget.c"
  #include "pnglib/pngmem.c"
  #include "pnglib/pngread.c"
  #include "pnglib/pngpread.c"
  #include "pnglib/pngrio.c"

  void png_do_expand_palette (png_row_infop, png_bytep, png_const_colorp, png_const_bytep, int);
  void png_do_expand (png_row_infop, png_bytep, png_const_color_16p);
  void png_do_chop (png_row_infop, png_bytep);
  void png_do_quantize (png_row_infop, png_bytep, png_const_bytep, png_const_bytep);
  void png_do_gray_to_rgb (png_row_infop, png_bytep);
  void png_do_unshift (png_row_infop, png_bytep, png_const_color_8p);
  void png_do_unpack (png_row_infop, png_bytep);
  int png_do_rgb_to_gray (png_structrp, png_row_infop, png_bytep);
  void png_do_compose (png_row_infop, png_bytep, png_structrp);
  void png_do_gamma (png_row_infop, png_bytep, png_structrp);
  void png_do_encode_alpha (png_row_infop, png_bytep, png_structrp);
  void png_do_scale_16_to_8 (png_row_infop, png_bytep);
  void png_do_expand_16 (png_row_infop, png_bytep);
  void png_do_read_filler (png_row_infop, png_bytep, png_uint_32, png_uint_32);
  void png_do_read_invert_alpha (png_row_infop, png_bytep);
  void png_do_read_swap_alpha (png_row_infop, png_bytep);

  #include "pnglib/pngrtran.c"
  #include "pnglib/pngrutil.c"
  #include "pnglib/pngset.c"
  #include "pnglib/pngtrans.c"
  #include "pnglib/pngwio.c"
  #include "pnglib/pngwrite.c"
  #include "pnglib/pngwtran.c"
  #include "pnglib/pngwutil.c"

  JUCE_END_IGNORE_WARNINGS_GCC_LIKE

#else
  extern "C"
  {
    #include <png.h>
    #include <pngconf.h>
  }
#endif
}

#undef max
#undef min
#undef fdopen

JUCE_END_IGNORE_WARNINGS_MSVC

//==============================================================================
namespace PNGHelpers
{
    using namespace pnglibNamespace;

    static void JUCE_CDECL writeDataCallback (png_structp png, png_bytep data, png_size_t length)
    {
        static_cast<OutputStream*> (png_get_io_ptr (png))->write (data, length);
    }

   #if ! JUCE_USING_COREIMAGE_LOADER
    static void JUCE_CDECL readCallback (png_structp png, png_bytep data, png_size_t length)
    {
        static_cast<InputStream*> (png_get_io_ptr (png))->read (data, (int) length);
    }

    struct PNGErrorStruct {};

    static void JUCE_CDECL errorCallback (png_structp p, png_const_charp)
    {
       #ifdef PNG_SETJMP_SUPPORTED
        setjmp(png_jmpbuf(p));
       #else
        longjmp (*(jmp_buf*) p->error_ptr, 1);
       #endif
    }

    static void JUCE_CDECL warningCallback (png_structp, png_const_charp) {}

    JUCE_BEGIN_IGNORE_WARNINGS_MSVC (4611)

    static bool readHeader (InputStream& in, png_structp pngReadStruct, png_infop pngInfoStruct, jmp_buf& errorJumpBuf,
                            png_uint_32& width, png_uint_32& height, int& bitDepth, int& colorType, int& interlaceType) noexcept
    {
        if (setjmp (errorJumpBuf) == 0)
        {
            // read the header..
            png_set_read_fn (pngReadStruct, &in, readCallback);

            png_read_info (pngReadStruct, pngInfoStruct);

            png_get_IHDR (pngReadStruct, pngInfoStruct,
                          &width, &height,
                          &bitDepth, &colorType,
                          &interlaceType, nullptr, nullptr);

            if (bitDepth == 16)
                png_set_strip_16 (pngReadStruct);

            if (colorType == PNG_COLOR_TYPE_PALETTE)
                png_set_expand (pngReadStruct);

            if (bitDepth < 8)
                png_set_expand (pngReadStruct);

            if (colorType == PNG_COLOR_TYPE_GRAY || colorType == PNG_COLOR_TYPE_GRAY_ALPHA)
                png_set_gray_to_rgb (pngReadStruct);

            return true;
        }

        return false;
    }

    static bool readImageData (png_structp pngReadStruct, png_infop pngInfoStruct, jmp_buf& errorJumpBuf, png_bytepp rows) noexcept
    {
        if (setjmp (errorJumpBuf) == 0)
        {
            if (png_get_valid (pngReadStruct, pngInfoStruct, PNG_INFO_tRNS))
                png_set_expand (pngReadStruct);

            png_set_add_alpha (pngReadStruct, 0xff, PNG_FILLER_AFTER);

            png_read_image (pngReadStruct, rows);
            png_read_end (pngReadStruct, pngInfoStruct);
            return true;
        }

        return false;
    }

    JUCE_END_IGNORE_WARNINGS_MSVC

    static Image createImageFromData (bool hasAlphaChan, int width, int height, png_bytepp rows)
    {
        // now convert the data to a juce image format..
        Image image (hasAlphaChan ? Image::ARGB : Image::RGB, width, height, hasAlphaChan);

        image.getProperties()->set ("originalImageHadAlpha", image.hasAlphaChannel());
        hasAlphaChan = image.hasAlphaChannel(); // (the native image creator may not give back what we expect)

        const Image::BitmapData destData (image, Image::BitmapData::writeOnly);

        for (int y = 0; y < (int) height; ++y)
        {
            const uint8* src = rows[y];
            uint8* dest = destData.getLinePointer (y);

            if (hasAlphaChan)
            {
                for (int i = (int) width; --i >= 0;)
                {
                    ((PixelARGB*) dest)->setARGB (src[3], src[0], src[1], src[2]);
                    ((PixelARGB*) dest)->premultiply();
                    dest += destData.pixelStride;
                    src += 4;
                }
            }
            else
            {
                for (int i = (int) width; --i >= 0;)
                {
                    ((PixelRGB*) dest)->setARGB (0, src[0], src[1], src[2]);
                    dest += destData.pixelStride;
                    src += 4;
                }
            }
        }

        return image;
    }

    static Image readImage (InputStream& in, png_structp pngReadStruct, png_infop pngInfoStruct)
    {
        jmp_buf errorJumpBuf;
        png_set_error_fn (pngReadStruct, &errorJumpBuf, errorCallback, warningCallback);

        png_uint_32 width = 0, height = 0;
        int bitDepth = 0, colorType = 0, interlaceType = 0;

        if (readHeader (in, pngReadStruct, pngInfoStruct, errorJumpBuf,
                        width, height, bitDepth, colorType, interlaceType))
        {
            // Load the image into a temp buffer..
            const size_t lineStride = width * 4;
            HeapBlock<uint8> tempBuffer (height * lineStride);
            HeapBlock<png_bytep> rows (height);

            for (size_t y = 0; y < height; ++y)
                rows[y] = (png_bytep) (tempBuffer + lineStride * y);

            png_bytep trans_alpha = nullptr;
            png_color_16p trans_color = nullptr;
            int num_trans = 0;
            png_get_tRNS (pngReadStruct, pngInfoStruct, &trans_alpha, &num_trans, &trans_color);

            if (readImageData (pngReadStruct, pngInfoStruct, errorJumpBuf, rows))
                return createImageFromData ((colorType & PNG_COLOR_MASK_ALPHA) != 0 || num_trans != 0,
                                            (int) width, (int) height, rows);
        }

        return Image();
    }

    static Image readImage (InputStream& in)
    {
        if (png_structp pngReadStruct = png_create_read_struct (PNG_LIBPNG_VER_STRING, nullptr, nullptr, nullptr))
        {
            if (png_infop pngInfoStruct = png_create_info_struct (pngReadStruct))
            {
                Image image (readImage (in, pngReadStruct, pngInfoStruct));
                png_destroy_read_struct (&pngReadStruct, &pngInfoStruct, nullptr);
                return image;
            }

            png_destroy_read_struct (&pngReadStruct, nullptr, nullptr);
        }

        return Image();
    }
   #endif
}

//==============================================================================
PNGImageFormat::PNGImageFormat()    {}
PNGImageFormat::~PNGImageFormat()   {}

String PNGImageFormat::getFormatName()                   { return "PNG"; }
bool PNGImageFormat::usesFileExtension (const File& f)   { return f.hasFileExtension ("png"); }

bool PNGImageFormat::canUnderstand (InputStream& in)
{
    const int bytesNeeded = 4;
    char header [bytesNeeded];

    return in.read (header, bytesNeeded) == bytesNeeded
            && header[1] == 'P'
            && header[2] == 'N'
            && header[3] == 'G';
}

#if JUCE_USING_COREIMAGE_LOADER
 Image juce_loadWithCoreImage (InputStream&);
#endif

Image PNGImageFormat::decodeImage (InputStream& in)
{
   #if JUCE_USING_COREIMAGE_LOADER
    return juce_loadWithCoreImage (in);
   #else
    return PNGHelpers::readImage (in);
   #endif
}

bool PNGImageFormat::writeImageToStream (const Image& image, OutputStream& out)
{
    using namespace pnglibNamespace;
    auto width = image.getWidth();
    auto height = image.getHeight();

    auto pngWriteStruct = png_create_write_struct (PNG_LIBPNG_VER_STRING, nullptr, nullptr, nullptr);

    if (pngWriteStruct == nullptr)
        return false;

    auto pngInfoStruct = png_create_info_struct (pngWriteStruct);

    if (pngInfoStruct == nullptr)
    {
        png_destroy_write_struct (&pngWriteStruct, nullptr);
        return false;
    }

    png_set_write_fn (pngWriteStruct, &out, PNGHelpers::writeDataCallback, nullptr);

    png_set_IHDR (pngWriteStruct, pngInfoStruct, (png_uint_32) width, (png_uint_32) height, 8,
                  image.hasAlphaChannel() ? PNG_COLOR_TYPE_RGB_ALPHA
                                          : PNG_COLOR_TYPE_RGB,
                  PNG_INTERLACE_NONE,
                  PNG_COMPRESSION_TYPE_BASE,
                  PNG_FILTER_TYPE_BASE);

    HeapBlock<uint8> rowData (width * 4);

    png_color_8 sig_bit;
    sig_bit.red   = 8;
    sig_bit.green = 8;
    sig_bit.blue  = 8;
    sig_bit.gray  = 0;
    sig_bit.alpha = 8;
    png_set_sBIT (pngWriteStruct, pngInfoStruct, &sig_bit);

    png_write_info (pngWriteStruct, pngInfoStruct);

    png_set_shift (pngWriteStruct, &sig_bit);
    png_set_packing (pngWriteStruct);

    const Image::BitmapData srcData (image, Image::BitmapData::readOnly);

    for (int y = 0; y < height; ++y)
    {
        uint8* dst = rowData;
        const uint8* src = srcData.getLinePointer (y);

        if (image.hasAlphaChannel())
        {
            for (int i = width; --i >= 0;)
            {
                PixelARGB p (*(const PixelARGB*) src);
                p.unpremultiply();

                *dst++ = p.getRed();
                *dst++ = p.getGreen();
                *dst++ = p.getBlue();
                *dst++ = p.getAlpha();
                src += srcData.pixelStride;
            }
        }
        else
        {
            for (int i = width; --i >= 0;)
            {
                *dst++ = ((const PixelRGB*) src)->getRed();
                *dst++ = ((const PixelRGB*) src)->getGreen();
                *dst++ = ((const PixelRGB*) src)->getBlue();
                src += srcData.pixelStride;
            }
        }

        png_bytep rowPtr = rowData;
        png_write_rows (pngWriteStruct, &rowPtr, 1);
    }

    png_write_end (pngWriteStruct, pngInfoStruct);
    png_destroy_write_struct (&pngWriteStruct, &pngInfoStruct);

    return true;
}

} // namespace juce