+// ----------------------------------------------------------------------------
+// reading PNGs
+// ----------------------------------------------------------------------------
+
+bool wxPNGHandler::DoCanRead( wxInputStream& stream )
+{
+ unsigned char hdr[4];
+
+ if ( !stream.Read(hdr, WXSIZEOF(hdr)) ) // it's ok to modify the stream position here
+ return false;
+
+ return memcmp(hdr, "\211PNG", WXSIZEOF(hdr)) == 0;
+}
+
+// convert data from RGB to wxImage format
+static
+void CopyDataFromPNG(wxImage *image,
+ unsigned char **lines,
+ png_uint_32 width,
+ png_uint_32 height,
+ int color_type)
+{
+ Transparency transparency = Transparency_None;
+
+ // only non NULL if transparency == Transparency_Alpha
+ unsigned char *alpha = NULL;
+
+ // RGB of the mask colour if transparency == Transparency_Mask
+ // (but init them anyhow to avoid compiler warnings)
+ unsigned char rMask = 0,
+ gMask = 0,
+ bMask = 0;
+
+ unsigned char *ptrDst = image->GetData();
+ if ( !(color_type & PNG_COLOR_MASK_COLOR) )
+ {
+ // grey image: GAGAGA... where G == grey component and A == alpha
+ for ( png_uint_32 y = 0; y < height; y++ )
+ {
+ const unsigned char *ptrSrc = lines[y];
+ for ( png_uint_32 x = 0; x < width; x++ )
+ {
+ unsigned char g = *ptrSrc++;
+ unsigned char a = *ptrSrc++;
+
+ // the first time we encounter a transparent pixel we must
+ // decide about what to do about them
+ 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
+ // only enough if we have alpha values of 0 and 0xff
+ // only, otherwisewe need the latter
+ transparency = CheckTransparency
+ (
+ lines,
+ x, y,
+ width, height,
+ 1
+ );
+
+ if ( transparency == Transparency_Mask )
+ {
+ // let's choose this colour for the mask: this is
+ // not a problem here as all the other pixels are
+ // grey, i.e. R == G == B which is not the case for
+ // this one so no confusion is possible
+ rMask = 0xff;
+ gMask = 0;
+ bMask = 0xff;
+ }
+ else // transparency == Transparency_Alpha
+ {
+ alpha = InitAlpha(image, x, y);
+ }
+ }
+
+ switch ( transparency )
+ {
+ case Transparency_Mask:
+ if ( IsTransparent(a) )
+ {
+ *ptrDst++ = rMask;
+ *ptrDst++ = gMask;
+ *ptrDst++ = bMask;
+ 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:
+ if ( alpha )
+ *alpha++ = a;
+ // fall through
+
+ case Transparency_None:
+ *ptrDst++ = g;
+ *ptrDst++ = g;
+ *ptrDst++ = g;
+ break;
+ }
+ }
+ }
+ }
+ else // colour image: RGBRGB...
+ {
+ for ( png_uint_32 y = 0; y < height; y++ )
+ {
+ const unsigned char *ptrSrc = lines[y];
+ for ( png_uint_32 x = 0; x < width; x++ )
+ {
+ unsigned char r = *ptrSrc++;
+ unsigned char g = *ptrSrc++;
+ unsigned char b = *ptrSrc++;
+ unsigned char a = *ptrSrc++;
+
+ // the logic here is the same as for the grey case except
+ // where noted
+ if ( !IsOpaque(a) && transparency == Transparency_None )
+ {
+ transparency = CheckTransparency
+ (
+ lines,
+ x, y,
+ width, height,
+ 3
+ );
+
+ if ( transparency == Transparency_Mask )
+ {
+ FindMaskColour(lines, width, height,
+ rMask, gMask, bMask);
+ }
+ else // transparency == Transparency_Alpha
+ {
+ alpha = InitAlpha(image, x, y);
+ }
+
+ }
+
+ switch ( transparency )
+ {
+ case Transparency_Mask:
+ if ( IsTransparent(a) )
+ {
+ *ptrDst++ = rMask;
+ *ptrDst++ = gMask;
+ *ptrDst++ = bMask;
+ 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") );
+
+ // 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++;
+ }
+ }
+
+ // fall through
+
+ case Transparency_Alpha:
+ if ( alpha )
+ *alpha++ = a;
+ // fall through
+
+ case Transparency_None:
+ *ptrDst++ = r;
+ *ptrDst++ = g;
+ *ptrDst++ = b;
+ break;
+ }
+ }
+ }
+ }
+
+ if ( transparency == Transparency_Mask )
+ {
+ image->SetMaskColour(rMask, gMask, bMask);
+ }
+}
projects / wxWidgets.git / blobdiff