// have transparent pixels, i.e. either Transparency_Alpha or Transparency_Mask
static Transparency
CheckTransparency(const unsigned char *ptr,
- png_uint_32 x, png_uint_32 y, png_uint_32 w, png_uint_32 h);
+ png_uint_32 x, png_uint_32 y, png_uint_32 w, png_uint_32 h,
+ size_t numColBytes);
// init the alpha channel for the image and fill it with 1s up to (x, y)
static unsigned char *InitAlpha(wxImage *image, png_uint_32 x, png_uint_32 y);
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
// ============================================================================
// ----------------------------------------------------------------------------
// 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
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
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;
// 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
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:
*ptrDst++ = g;
*ptrDst++ = g;
break;
-
- case Transparency_Mask:
- *ptrDst++ = rMask;
- *ptrDst++ = bMask;
- *ptrDst++ = gMask;
}
}
}
// 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
(
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:
*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;
}
}
}
projects / wxWidgets.git / blobdiff