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Improved palette handling with saving PNG files.

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Instead of converting alpha to a mask an attempt is made to write a palettised PNG file with an ARGB palette using a maximum of 256 transparency values where formerly just up to one was supported. GIF images with 256 colours and transparency can now also be saved as a palettised PNG instead of true colour, making the image a lot smaller.

Applied (modified) patch by troelsk. Closes #12850.



git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@67101 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
This commit is contained in:
Dimitri Schoolwerth 2011-03-01 21:29:17 +00:00
parent 548fa9c1eb
commit 8529b0b909
2 changed files with 164 additions and 177 deletions
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244
src/common/imagpng.cpp
View File

@ -646,27 +646,42 @@ error:
}
// ----------------------------------------------------------------------------
// SaveFile() helpers
// SaveFile() palette helpers
// ----------------------------------------------------------------------------
#if wxUSE_PALETTE
typedef wxLongToLongHashMap PaletteMap;
static int PaletteFind(const png_color& clr, const png_color *pal, int palCount)
static unsigned long PaletteMakeKey(const png_color_8& clr)
{
for (int i = 0; i < palCount; ++i)
{
if ( (clr.red == pal[i].red)
&& (clr.green == pal[i].green)
&& (clr.blue == pal[i].blue))
{
return i;
}
}
return wxNOT_FOUND;
return (wxImageHistogram::MakeKey(clr.red, clr.green, clr.blue) << 8) | clr.alpha;
}
#endif // wxUSE_PALETTE
static long PaletteFind(const PaletteMap& palette, const png_color_8& clr)
{
unsigned long value = PaletteMakeKey(clr);
PaletteMap::const_iterator it = palette.find(value);
return (it != palette.end()) ? it->second : wxNOT_FOUND;
}
static long PaletteAdd(PaletteMap *palette, const png_color_8& clr)
{
unsigned long value = PaletteMakeKey(clr);
PaletteMap::const_iterator it = palette->find(value);
size_t index;
if (it == palette->end())
{
index = palette->size();
(*palette)[value] = index;
}
else
{
index = it->second;
}
return index;
}
// ----------------------------------------------------------------------------
// writing PNGs
@ -720,6 +735,9 @@ bool wxPNGHandler::SaveFile( wxImage *image, wxOutputStream& stream, bool verbos
// explanation why this line is mandatory
png_set_write_fn( png_ptr, &wxinfo, wx_PNG_stream_writer, NULL);
const int iHeight = image->GetHeight();
const int iWidth = image->GetWidth();
const bool bHasPngFormatOption
= image->HasOption(wxIMAGE_OPTION_PNG_FORMAT);
@ -730,49 +748,86 @@ bool wxPNGHandler::SaveFile( wxImage *image, wxOutputStream& stream, bool verbos
bool bHasAlpha = image->HasAlpha();
bool bHasMask = image->HasMask();
bool bUsePalette = iColorType == wxPNG_TYPE_PALETTE
#if wxUSE_PALETTE
/*
Only save as an indexed image if the number of palette entries does not
exceed libpng's limit (256).
We assume here that we will need an extra palette entry if there's an
alpha or mask, regardless of whether a possibly needed conversion from
alpha to a mask fails (unlikely), or whether the mask colour already
can be found in the palette (more likely). In the latter case an extra
palette entry would not be required later on and the image could actually
be saved as a palettised PNG (instead now it will be saved as true colour).
A little bit of precision is lost, but at the benefit of a lot more
simplified code.
*/
bool bUsePalette =
(!bHasPngFormatOption || iColorType == wxPNG_TYPE_PALETTE)
&& image->HasPalette()
&& image->GetPalette().GetColoursCount()
+ ((bHasAlpha || bHasMask) ? 1 : 0) <= PNG_MAX_PALETTE_LENGTH;
|| (!bHasPngFormatOption && image->HasPalette() )
#endif
;
wxImage temp_image(*image);
if (bUsePalette && image->HasAlpha() && !bHasMask)
png_color_8 mask;
if (bHasMask)
{
/*
Only convert alpha to mask if saving as a palettised image was
explicitly requested. We don't want to lose alpha's precision
by converting to a mask just to be able to save palettised.
*/
if (iColorType == wxPNG_TYPE_PALETTE
&& temp_image.ConvertAlphaToMask())
mask.red = image->GetMaskRed();
mask.green = image->GetMaskGreen();
mask.blue = image->GetMaskBlue();
mask.alpha = 0;
mask.gray = 0;
}
PaletteMap palette;
if (bUsePalette)
{
png_color png_rgb [PNG_MAX_PALETTE_LENGTH];
png_byte png_trans[PNG_MAX_PALETTE_LENGTH];
const unsigned char *pColors = image->GetData();
const unsigned char* pAlpha = image->GetAlpha();
if (bHasMask && !pAlpha)
{
image = &temp_image;
bHasMask = true;
bHasAlpha = image->HasAlpha();
// Mask must be first
PaletteAdd(&palette, mask);
}
else
for (int y = 0; y < iHeight; y++)
{
bUsePalette = false;
iColorType = wxPNG_TYPE_COLOUR;
for (int x = 0; x < iWidth; x++)
{
png_color_8 rgba;
rgba.red = *pColors++;
rgba.green = *pColors++;
rgba.blue = *pColors++;
rgba.gray = 0;
rgba.alpha = (pAlpha && !bHasMask) ? *pAlpha++ : 0;
// save in our palette
long index = PaletteAdd(&palette, rgba);
if (index < PNG_MAX_PALETTE_LENGTH)
{
// save in libpng's palette
png_rgb[index].red = rgba.red;
png_rgb[index].green = rgba.green;
png_rgb[index].blue = rgba.blue;
png_trans[index] = rgba.alpha;
}
else
{
bUsePalette = false;
break;
}
}
}
if (bUsePalette)
{
png_set_PLTE(png_ptr, info_ptr, png_rgb, palette.size());
if (bHasMask && !pAlpha)
{
wxASSERT(PaletteFind(palette, mask) == 0);
png_trans[0] = 0;
png_set_tRNS(png_ptr, info_ptr, png_trans, 1, NULL);
}
else if (pAlpha && !bHasMask)
{
png_set_tRNS(png_ptr, info_ptr, png_trans, palette.size(), NULL);
}
}
}
#else
bool bUsePalette = false;
#endif // wxUSE_PALETTE
/*
If saving palettised was requested but it was decided we can't use a
@ -785,26 +840,14 @@ bool wxPNGHandler::SaveFile( wxImage *image, wxOutputStream& stream, bool verbos
bool bUseAlpha = !bUsePalette && (bHasAlpha || bHasMask);
png_color mask;
if (bHasMask)
{
mask.red = image->GetMaskRed();
mask.green = image->GetMaskGreen();
mask.blue = image->GetMaskBlue();
}
int iPngColorType;
#if wxUSE_PALETTE
if (bUsePalette)
{
iPngColorType = PNG_COLOR_TYPE_PALETTE;
iColorType = wxPNG_TYPE_PALETTE;
}
else
#endif // wxUSE_PALETTE
if ( iColorType==wxPNG_TYPE_COLOUR )
else if ( iColorType==wxPNG_TYPE_COLOUR )
{
iPngColorType = bUseAlpha ? PNG_COLOR_TYPE_RGB_ALPHA
: PNG_COLOR_TYPE_RGB;
@ -839,62 +882,6 @@ bool wxPNGHandler::SaveFile( wxImage *image, wxOutputStream& stream, bool verbos
PNG_INTERLACE_NONE, PNG_COMPRESSION_TYPE_BASE,
PNG_FILTER_TYPE_BASE);
#if wxUSE_PALETTE
png_colorp palette = NULL;
int numPalette = 0;
if (bUsePalette)
{
const wxPalette& pal = image->GetPalette();
const int palCount = pal.GetColoursCount();
palette = (png_colorp) malloc(
(palCount + 1 /*headroom for trans */) * sizeof(png_color));
if (!palette)
{
png_destroy_write_struct( &png_ptr, (png_infopp)NULL );
if (verbose)
{
wxLogError(_("Couldn't save PNG image."));
}
return false;
}
for (int i = 0; i < palCount; ++i)
{
pal.GetRGB(i, &palette[i].red, &palette[i].green, &palette[i].blue);
}
numPalette = palCount;
if (bHasMask)
{
int index = PaletteFind(mask, palette, numPalette);
if (index)
{
if (index == wxNOT_FOUND)
{
numPalette++;
index = palCount;
palette[index] = mask;
}
wxSwap(palette[0], palette[index]);
}
png_byte trans = 0;
png_set_tRNS(png_ptr, info_ptr, &trans, 1, NULL);
}
png_set_PLTE(png_ptr, info_ptr, palette, numPalette);
free (palette);
palette = NULL;
// Let palette point to libpng's copy of the palette.
(void) png_get_PLTE(png_ptr, info_ptr, &palette, &numPalette);
}
#endif // wxUSE_PALETTE
int iElements;
png_color_8 sig_bit;
@ -911,7 +898,7 @@ bool wxPNGHandler::SaveFile( wxImage *image, wxOutputStream& stream, bool verbos
iElements = 1;
}
if ( iPngColorType & PNG_COLOR_MASK_ALPHA )
if ( bUseAlpha )
{
sig_bit.alpha = (png_byte)iBitDepth;
iElements++;
@ -960,22 +947,22 @@ bool wxPNGHandler::SaveFile( wxImage *image, wxOutputStream& stream, bool verbos
return false;
}
unsigned char *
pAlpha = (unsigned char *)(bHasAlpha ? image->GetAlpha() : NULL);
int iHeight = image->GetHeight();
int iWidth = image->GetWidth();
const unsigned char *
pAlpha = (const unsigned char *)(bHasAlpha ? image->GetAlpha() : NULL);
unsigned char *pColors = image->GetData();
const unsigned char *pColors = image->GetData();
for (int y = 0; y != iHeight; ++y)
{
unsigned char *pData = data;
for (int x = 0; x != iWidth; x++)
{
png_color clr;
png_color_8 clr;
clr.red = *pColors++;
clr.green = *pColors++;
clr.blue = *pColors++;
clr.gray = 0;
clr.alpha = (bUsePalette && pAlpha) ? *pAlpha++ : 0; // use with wxPNG_TYPE_PALETTE only
switch ( iColorType )
{
@ -1016,12 +1003,9 @@ bool wxPNGHandler::SaveFile( wxImage *image, wxOutputStream& stream, bool verbos
*pData++ = 0;
break;
#if wxUSE_PALETTE
case wxPNG_TYPE_PALETTE:
*pData++ = (unsigned char) PaletteFind(clr,
palette, numPalette);
*pData++ = (unsigned char) PaletteFind(palette, clr);
break;
#endif // wxUSE_PALETTE
}
if ( bUseAlpha )

97
tests/image/image.cpp
View File

@ -71,6 +71,7 @@ private:
CPPUNIT_TEST( SizeImage );
CPPUNIT_TEST( CompareLoadedImage );
CPPUNIT_TEST( CompareSavedImage );
CPPUNIT_TEST( SavePNG );
CPPUNIT_TEST( SaveAnimatedGIF );
CPPUNIT_TEST( ReadCorruptedTGA );
CPPUNIT_TEST( GIFComment );
@ -82,6 +83,7 @@ private:
void SizeImage();
void CompareLoadedImage();
void CompareSavedImage();
void SavePNG();
void SaveAnimatedGIF();
void ReadCorruptedTGA();
void GIFComment();
@ -1023,77 +1025,78 @@ void ImageTestCase::CompareSavedImage()
CompareImage(*handler, expected24);
CompareImage(*handler, expected32, wxIMAGE_HAVE_ALPHA);
}
}
void ImageTestCase::SavePNG()
{
wxImage expected24("horse.png");
CPPUNIT_ASSERT( expected24.IsOk() );
#if wxUSE_PALETTE
CPPUNIT_ASSERT( !expected24.HasPalette() );
#endif // #if wxUSE_PALETTE
wxImage expected8 = expected24.ConvertToGreyscale();
/*
horse.png converted to greyscale should be saved without a palette.
*/
CompareImage(*wxImage::FindHandler(wxBITMAP_TYPE_PNG), expected8);
/*
But if we explicitly ask for trying to save with a palette, it should work.
*/
expected8.SetOption(wxIMAGE_OPTION_PNG_FORMAT, wxPNG_TYPE_PALETTE);
CompareImage(*wxImage::FindHandler(wxBITMAP_TYPE_PNG),
expected8, wxIMAGE_HAVE_PALETTE);
expected8.LoadFile("horse.gif");
CPPUNIT_ASSERT( expected8.IsOk() );
CPPUNIT_ASSERT( expected8.LoadFile("horse.gif") );
#if wxUSE_PALETTE
CPPUNIT_ASSERT( expected8.HasPalette() );
#endif // #if wxUSE_PALETTE
CompareImage(*wxImage::FindHandler(wxBITMAP_TYPE_PNG),
expected8, wxIMAGE_HAVE_PALETTE);
/*
Add alpha to the image in such a way that there will still be a maximum
of 256 unique RGBA combinations. This should result in a saved
PNG image still being palettised and having alpha.
*/
expected8.SetAlpha();
width = expected8.GetWidth();
height = expected8.GetHeight();
int x, y;
const int width = expected8.GetWidth();
const int height = expected8.GetHeight();
for (y = 0; y < height; ++y)
{
for (x = 0; x < width; ++x)
{
expected8.SetAlpha(x, y, (x*y) & wxIMAGE_ALPHA_OPAQUE);
expected8.SetAlpha(x, y, expected8.GetRed(x, y));
}
}
/*
Explicitly make known we want a palettised PNG. If we don't then this
particular image gets saved as a true colour image because there's an
alpha channel present and the PNG saver prefers to keep the alpha over
saving as a palettised image that has alpha converted to a mask.
*/
expected8.SetOption(wxIMAGE_OPTION_PNG_FORMAT, wxPNG_TYPE_PALETTE);
CompareImage(*wxImage::FindHandler(wxBITMAP_TYPE_PNG),
expected8, wxIMAGE_HAVE_ALPHA|wxIMAGE_HAVE_PALETTE);
/*
The image contains 256 indexed colours and needs another palette entry
for storing the transparency index. This results in wanting 257 palette
entries but that amount is not supported by PNG, as such this image
should not contain a palette (but still have alpha) and be stored as a
true colour image instead.
Now change the alpha of the first pixel so that we can't save palettised
anymore because there will be 256+1 entries which is beyond PNGs limit
of 256 entries.
*/
expected8.SetAlpha(0, 0, 1);
CompareImage(*wxImage::FindHandler(wxBITMAP_TYPE_PNG),
expected8, wxIMAGE_HAVE_ALPHA);
#if wxUSE_PALETTE
/*
Now do the same test again but remove one (random) palette entry. This
should result in saving the PNG with a palette.
Even if we explicitly ask for saving palettised it should not be done.
*/
unsigned char red[256], green[256], blue[256];
const wxPalette& pal = expected8.GetPalette();
const int paletteCount = pal.GetColoursCount();
for (i = 0; i < paletteCount; ++i)
{
expected8.GetPalette().GetRGB(i, &red[i], &green[i], &blue[i]);
}
wxPalette newPal(paletteCount - 1, red, green, blue);
expected8.Replace(
red[paletteCount-1], green[paletteCount-1], blue[paletteCount-1],
red[paletteCount-2], green[paletteCount-2], blue[paletteCount-2]);
expected8.SetPalette(newPal);
wxImage ref8 = expected8;
/*
Convert the alpha channel to a mask like the PNG saver does. Also convert
the colour used for transparency from 1,0,0 to 2,0,0. The latter gets
done by the PNG loader in search of an unused colour to use for
transparency (this should be fixed).
*/
ref8.ConvertAlphaToMask();
ref8.Replace(1, 0, 0, 2, 0, 0);
expected8.SetOption(wxIMAGE_OPTION_PNG_FORMAT, wxPNG_TYPE_PALETTE);
CompareImage(*wxImage::FindHandler(wxBITMAP_TYPE_PNG),
expected8, wxIMAGE_HAVE_PALETTE, &ref8);
#endif
expected8, wxIMAGE_HAVE_ALPHA);
}
void ImageTestCase::SaveAnimatedGIF()