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many fixes for PNG reading after recent alpha changes; grey scale images reading was in particular broken

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git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@20581 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
This commit is contained in:
Vadim Zeitlin
2003-05-11 10:49:27 +00:00
parent edb57eaebe
commit c9fcf5817f
1 changed files with 79 additions and 37 deletions
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116
src/common/imagpng.cpp
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@@ -86,6 +86,20 @@ static void
FindMaskColour(unsigned char **lines, png_uint_32 width, png_uint_32 height,
unsigned char& rMask, unsigned char& gMask, unsigned char& bMask);
// is the pixel with this value of alpha a fully opaque one?
static inline
bool IsOpaque(unsigned char a)
{
return a == 0xff;
}
// is the pixel with this value of alpha a fully transparent one?
static inline
bool IsTransparent(unsigned char a)
{
return !a;
}
// ============================================================================
// wxPNGHandler implementation
// ============================================================================
@@ -191,9 +205,9 @@ PNGLINKAGEMODE wx_png_warning(png_structp png_ptr, png_const_charp message)
// ----------------------------------------------------------------------------
// determine the kind of transparency we need for this image: if the only alpha
// values it has are 0 and 0xff then we can simply create a mask for it, we
// should be ok with a simple mask but otherwise we need a full blown alpha
// channel in wxImage
// values it has are 0 (transparent) and 0xff (opaque) then we can simply
// create a mask for it, we should be ok with a simple mask but otherwise we
// need a full blown alpha channel in wxImage
//
// parameters:
// ptr the start of the data to examine
@@ -206,24 +220,30 @@ CheckTransparency(const unsigned char *ptr,
png_uint_32 x, png_uint_32 y, png_uint_32 w, png_uint_32 h,
size_t numColBytes)
{
// we start from (x + 1, y)
x++;
// suppose that a mask will suffice and check all the remaining alpha
// values to see if it does
unsigned char a2;
unsigned const char *ptr2 = ptr;
for ( png_uint_32 y2 = y; y2 < h; y2++ )
{
for ( png_uint_32 x2 = x + 1; x2 < w; x2++ )
for ( png_uint_32 x2 = x; x2 < w; x2++ )
{
// skip the grey byte
// skip the grey or colour byte(s)
ptr2 += numColBytes;
a2 = *ptr2++;
if ( a2 && a2 != 0xff )
unsigned char a2 = *ptr2++;
if ( !IsTransparent(a2) && !IsOpaque(a2) )
{
// not fully opaque nor fully transparent, hence need alpha
return Transparency_Alpha;
}
}
// during the next loop iteration check all the pixels in the row
x = 0;
}
// mask will be enough
@@ -238,13 +258,11 @@ unsigned char *InitAlpha(wxImage *image, png_uint_32 x, png_uint_32 y)
unsigned char *alpha = image->GetAlpha();
// set alpha for the pixels we had so far
for ( png_uint_32 y2 = 0; y2 <= y; y2++ )
png_uint_32 end = y * image->GetWidth() + x;
for ( png_uint_32 i = 0; i < end; i++ )
{
for ( png_uint_32 x2 = 0; x2 < x; x2++ )
{
// all the previous pixels were opaque
*alpha++ = 0xff;
}
// all the previous pixels were opaque
*alpha++ = 0xff;
}
return alpha;
@@ -339,7 +357,7 @@ void CopyDataFromPNG(wxImage *image,
// the first time we encounter a transparent pixel we must
// decide about what to do about them
if ( a != 0xff && transparency == Transparency_None )
if ( !IsOpaque(a) && transparency == Transparency_None )
{
// we'll need at least the mask for this image and
// maybe even full alpha channel info: the former is
@@ -371,8 +389,25 @@ void CopyDataFromPNG(wxImage *image,
switch ( transparency )
{
case Transparency_Mask:
if ( IsTransparent(a) )
{
*ptrDst++ = rMask;
*ptrDst++ = bMask;
*ptrDst++ = gMask;
break;
}
// else: !transparent
// must be opaque then as otherwise we shouldn't be
// using the mask at all
wxASSERT_MSG( IsOpaque(a), _T("logic error") );
// fall through
case Transparency_Alpha:
*alpha++ = a;
if ( alpha )
*alpha++ = a;
// fall through
case Transparency_None:
@@ -380,11 +415,6 @@ void CopyDataFromPNG(wxImage *image,
*ptrDst++ = g;
*ptrDst++ = g;
break;
case Transparency_Mask:
*ptrDst++ = rMask;
*ptrDst++ = bMask;
*ptrDst++ = gMask;
}
}
}
@@ -403,7 +433,7 @@ void CopyDataFromPNG(wxImage *image,
// the logic here is the same as for the grey case except
// where noted
if ( a != 0xff && transparency == Transparency_None )
if ( !IsOpaque(a) && transparency == Transparency_None )
{
transparency = CheckTransparency
(
@@ -427,8 +457,34 @@ void CopyDataFromPNG(wxImage *image,
switch ( transparency )
{
case Transparency_Mask:
if ( IsTransparent(a) )
{
// if we couldn't find a unique colour for the mask, we
// can have real pixels with the same value as the mask
// and it's better to slightly change their colour than
// to make them transparent
if ( r == rMask && g == gMask && b == bMask )
{
r++;
}
*ptrDst++ = rMask;
*ptrDst++ = bMask;
*ptrDst++ = gMask;
break;
}
// else: !transparent
// must be opaque then as otherwise we shouldn't be
// using the mask at all
wxASSERT_MSG( IsOpaque(a), _T("logic error") );
// fall through
case Transparency_Alpha:
*alpha++ = a;
if ( alpha )
*alpha++ = a;
// fall through
case Transparency_None:
@@ -436,20 +492,6 @@ void CopyDataFromPNG(wxImage *image,
*ptrDst++ = g;
*ptrDst++ = b;
break;
case Transparency_Mask:
// if we couldn't find a unique colour for the mask, we
// can have real pixels with the same value as the mask
// and it's better to slightly change their colour than
// to make them transparent
if ( r == rMask && g == gMask && b == bMask )
{
r++;
}
*ptrDst++ = rMask;
*ptrDst++ = bMask;
*ptrDst++ = gMask;
}
}
}