From: Vadim Zeitlin Date: Mon, 3 Mar 2003 20:39:50 +0000 (+0000) Subject: added support for reading alpha channel X-Git-Url: https://git.saurik.com/wxWidgets.git/commitdiff_plain/27bb2b7cea271d91e272452ff361f948e38dc539 added support for reading alpha channel git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@19456 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775 --- diff --git a/src/common/imagpng.cpp b/src/common/imagpng.cpp index 653c4effc8..1b8e201718 100644 --- a/src/common/imagpng.cpp +++ b/src/common/imagpng.cpp @@ -1,5 +1,5 @@ ///////////////////////////////////////////////////////////////////////////// -// Name: imagepng.cpp +// Name: src/common/imagepng.cpp // Purpose: wxImage PNG handler // Author: Robert Roebling // RCS-ID: $Id$ @@ -7,10 +7,18 @@ // Licence: wxWindows licence ///////////////////////////////////////////////////////////////////////////// +// ============================================================================ +// declarations +// ============================================================================ + #ifdef __GNUG__ #pragma implementation "imagpng.h" #endif +// ---------------------------------------------------------------------------- +// headers +// ---------------------------------------------------------------------------- + // For compilers that support precompilation, includes "wx.h". #include "wx/wxprec.h" @@ -44,13 +52,42 @@ #endif #endif -#ifdef __WXMSW__ -#include -#endif +// ---------------------------------------------------------------------------- +// constants +// ---------------------------------------------------------------------------- + +// image can not have any transparent pixels at all, have only 100% opaque +// and/or 100% transparent pixels in which case a simple mask is enough to +// store this information in wxImage or have a real alpha channel in which case +// we need to have it in wxImage as well +enum Transparency +{ + Transparency_None, + Transparency_Mask, + Transparency_Alpha +}; + +// ---------------------------------------------------------------------------- +// local functions +// ---------------------------------------------------------------------------- + +// return the kind of transparency needed for this image assuming that it does +// 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); + +// 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); + +// find a free colour for the mask in the PNG data array +static void +FindMaskColour(unsigned char **lines, png_uint_32 width, png_uint_32 height, + unsigned char& rMask, unsigned char& gMask, unsigned char& bMask); -//----------------------------------------------------------------------------- -// wxPNGHandler -//----------------------------------------------------------------------------- +// ============================================================================ +// wxPNGHandler implementation +// ============================================================================ IMPLEMENT_DYNAMIC_CLASS(wxPNGHandler,wxImageHandler) @@ -72,18 +109,18 @@ IMPLEMENT_DYNAMIC_CLASS(wxPNGHandler,wxImageHandler) // VS: wxPNGInfoStruct declared below is a hack that needs some explanation. -// First, let me describe what's the problem: libpng uses jmp_buf in -// its png_struct structure. Unfortunately, this structure is -// compiler-specific and may vary in size, so if you use libpng compiled +// First, let me describe what's the problem: libpng uses jmp_buf in +// its png_struct structure. Unfortunately, this structure is +// compiler-specific and may vary in size, so if you use libpng compiled // as DLL with another compiler than the main executable, it may not work -// (this is for example the case with wxMGL port and SciTech MGL library +// (this is for example the case with wxMGL port and SciTech MGL library // that provides custom runtime-loadable libpng implementation with jmpbuf -// disabled altogether). Luckily, it is still possible to use setjmp() & +// disabled altogether). Luckily, it is still possible to use setjmp() & // longjmp() as long as the structure is not part of png_struct. // // Sadly, there's no clean way to attach user-defined data to png_struct. // There is only one customizable place, png_struct.io_ptr, which is meant -// only for I/O routines and is set with png_set_read_fn or +// only for I/O routines and is set with png_set_read_fn or // png_set_write_fn. The hacky part is that we use io_ptr to store // a pointer to wxPNGInfoStruct that holds I/O structures _and_ jmp_buf. @@ -91,7 +128,7 @@ struct wxPNGInfoStruct { jmp_buf jmpbuf; bool verbose; - + union { wxInputStream *in; @@ -101,6 +138,9 @@ struct wxPNGInfoStruct #define WX_PNG_INFO(png_ptr) ((wxPNGInfoStruct*)png_get_io_ptr(png_ptr)) +// ---------------------------------------------------------------------------- +// helper functions +// ---------------------------------------------------------------------------- extern "C" { @@ -145,20 +185,285 @@ PNGLINKAGEMODE wx_png_warning(png_structp png_ptr, png_const_charp message) } // extern "C" +// ---------------------------------------------------------------------------- +// LoadFile() helpers +// ---------------------------------------------------------------------------- + +Transparency +CheckTransparency(const unsigned char *ptr, + png_uint_32 x, png_uint_32 y, png_uint_32 w, png_uint_32 h) +{ + // suppose that a mask will suffice + Transparency transparency = Transparency_Mask; + + // 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++ ) + { + // skip the grey byte + a2 = *++ptr2; + + if ( a2 && a2 != 0xff ) + { + // not fully opeaque nor fully transparent, hence need alpha + transparency = Transparency_Alpha; + break; + } + + ++ptr2; + } + + if ( transparency == Transparency_Alpha ) + { + // no need to continue + break; + } + } + + return transparency; +} + +unsigned char *InitAlpha(wxImage *image, png_uint_32 x, png_uint_32 y) +{ + // create alpha channel + image->SetAlpha(); + + unsigned char *alpha = image->GetAlpha(); + + // set alpha for the pixels we had so far + for ( png_uint_32 y2 = 0; y2 <= y; y2++ ) + { + for ( png_uint_32 x2 = 0; x2 < x; x2++ ) + { + // all the previous pixels were opaque + *alpha++ = 0xff; + } + } + + return alpha; +} + +void +FindMaskColour(unsigned char **lines, png_uint_32 width, png_uint_32 height, + unsigned char& rMask, unsigned char& gMask, unsigned char& bMask) +{ + // choosing the colour for the mask is more + // difficult: we need to iterate over the entire + // image for this in order to choose an unused + // colour (this is not very efficient but what else + // can we do?) + wxImageHistogram h; + unsigned nentries = 0; + unsigned char r2, g2, b2; + for ( png_uint_32 y2 = 0; y2 < height; y2++ ) + { + const unsigned char *p = lines[y2]; + for ( png_uint_32 x2 = 0; x2 < width; x2++ ) + { + r2 = *p++; + g2 = *p++; + b2 = *p++; + + wxImageHistogramEntry& + entry = h[wxImageHistogram:: MakeKey(r2, g2, b2)]; + + if ( entry.value++ == 0 ) + entry.index = nentries++; + } + } + + if ( !h.FindFirstUnusedColour(&rMask, &gMask, &bMask) ) + { + wxLogWarning(_("Too many colours in PNG, the image may be slightly blurred.")); + + // use a fixed mask colour and we'll fudge + // the real pixels with this colour (see + // below) + rMask = 0xfe; + gMask = 0; + bMask = 0xff; + } +} + +// ---------------------------------------------------------------------------- +// reading PNGs +// ---------------------------------------------------------------------------- + +bool wxPNGHandler::DoCanRead( wxInputStream& stream ) +{ + unsigned char hdr[4]; + + if ( !stream.Read(hdr, WXSIZEOF(hdr)) ) + 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 ( a != 0xff && 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(ptrSrc, x, y, + width, height); + + 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_Alpha: + *alpha++ = a; + // fall through + + case Transparency_None: + *ptrDst++ = g; + *ptrDst++ = g; + *ptrDst++ = g; + break; + + case Transparency_Mask: + *ptrDst++ = rMask; + *ptrDst++ = bMask; + *ptrDst++ = gMask; + } + } + } + } + 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 ( a != 0xff && transparency == Transparency_None ) + { + transparency = CheckTransparency(ptrSrc, x, y, + width, height); + + if ( transparency == Transparency_Mask ) + { + FindMaskColour(lines, width, height, + rMask, gMask, bMask); + } + else // transparency == Transparency_Alpha + { + alpha = InitAlpha(image, x, y); + } + + } + + switch ( transparency ) + { + case Transparency_Alpha: + *alpha++ = a; + // fall through + + case Transparency_None: + *ptrDst++ = r; + *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; + } + } + } + } + + if ( transparency == Transparency_Mask ) + { + image->SetMaskColour(rMask, gMask, bMask); + } +} + // temporarily disable the warning C4611 (interaction between '_setjmp' and // C++ object destruction is non-portable) - I don't see any dtors here #ifdef __VISUALC__ #pragma warning(disable:4611) #endif /* VC++ */ -bool wxPNGHandler::LoadFile( wxImage *image, wxInputStream& stream, bool verbose, int WXUNUSED(index) ) +bool +wxPNGHandler::LoadFile(wxImage *image, + wxInputStream& stream, + bool verbose, + int WXUNUSED(index)) { // VZ: as this function uses setjmp() the only fool proof error handling // method is to use goto (setjmp is not really C++ dtors friendly...) - unsigned char **lines; - unsigned int i; - png_infop info_ptr = (png_infop) NULL; + unsigned char **lines = NULL; + png_infop info_ptr = (png_infop) NULL; wxPNGInfoStruct wxinfo; wxinfo.verbose = verbose; @@ -171,7 +476,7 @@ bool wxPNGHandler::LoadFile( wxImage *image, wxInputStream& stream, bool verbose (png_error_ptr) NULL, (png_error_ptr) NULL ); if (!png_ptr) - goto error_nolines; + goto error; png_set_error_fn(png_ptr, (png_voidp)NULL, wx_png_error, wx_png_warning); @@ -181,16 +486,13 @@ bool wxPNGHandler::LoadFile( wxImage *image, wxInputStream& stream, bool verbose info_ptr = png_create_info_struct( png_ptr ); if (!info_ptr) - goto error_nolines; + goto error; if (setjmp(wxinfo.jmpbuf)) - goto error_nolines; - - if (info_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA) - goto error_nolines; + goto error; - png_uint_32 width,height; - int bit_depth,color_type,interlace_type; + png_uint_32 i, width, height; + int bit_depth, color_type, interlace_type; png_read_info( png_ptr, info_ptr ); png_get_IHDR( png_ptr, info_ptr, &width, &height, &bit_depth, &color_type, &interlace_type, (int*) NULL, (int*) NULL ); @@ -211,11 +513,11 @@ bool wxPNGHandler::LoadFile( wxImage *image, wxInputStream& stream, bool verbose image->Create( (int)width, (int)height ); if (!image->Ok()) - goto error_nolines; + goto error; lines = (unsigned char **)malloc( (size_t)(height * sizeof(unsigned char *)) ); - if (lines == NULL) - goto error_nolines; + if ( !lines ) + goto error; for (i = 0; i < height; i++) { @@ -227,87 +529,20 @@ bool wxPNGHandler::LoadFile( wxImage *image, wxInputStream& stream, bool verbose } } - // loaded successfully! - { - int transp = 0; - png_read_image( png_ptr, lines ); - png_read_end( png_ptr, info_ptr ); - png_destroy_read_struct( &png_ptr, &info_ptr, (png_infopp) NULL ); - unsigned char *ptr = image->GetData(); - if ((color_type == PNG_COLOR_TYPE_GRAY) || - (color_type == PNG_COLOR_TYPE_GRAY_ALPHA)) - { - for (unsigned int y = 0; y < height; y++) - { - unsigned char *ptr2 = lines[y]; - for (unsigned int x = 0; x < width; x++) - { - unsigned char r = *ptr2++; - unsigned char a = *ptr2++; - if (a < 128) - { - *ptr++ = 255; - *ptr++ = 0; - *ptr++ = 255; - transp = 1; - } - else - { - *ptr++ = r; - *ptr++ = r; - *ptr++ = r; - } - } - } - } - else - { - for (unsigned int y = 0; y < height; y++) - { - unsigned char *ptr2 = lines[y]; - for (unsigned int x = 0; x < width; x++) - { - unsigned char r = *ptr2++; - unsigned char g = *ptr2++; - unsigned char b = *ptr2++; - unsigned char a = *ptr2++; - if (a < 128) - { - *ptr++ = 255; - *ptr++ = 0; - *ptr++ = 255; - transp = 1; - } - else - { - if ((r == 255) && (g == 0) && (b == 255)) r = 254; - *ptr++ = r; - *ptr++ = g; - *ptr++ = b; - } - } - } - } + png_read_image( png_ptr, lines ); + png_read_end( png_ptr, info_ptr ); + png_destroy_read_struct( &png_ptr, &info_ptr, (png_infopp) NULL ); - for ( unsigned int j = 0; j < height; j++ ) - free( lines[j] ); - free( lines ); + // loaded successfully, now init wxImage with this data + CopyDataFromPNG(image, lines, width, height, color_type); - if (transp) - { - image->SetMaskColour( 255, 0, 255 ); - } - else - { - image->SetMask( FALSE ); - } - } + for ( i = 0; i < height; i++ ) + free( lines[i] ); + free( lines ); return TRUE; - error_nolines: - lines = NULL; // called from before it was set - error: +error: if (verbose) wxLogError(_("Couldn't load a PNG image - file is corrupted or not enough memory.")); @@ -334,6 +569,10 @@ bool wxPNGHandler::LoadFile( wxImage *image, wxInputStream& stream, bool verbose return FALSE; } +// ---------------------------------------------------------------------------- +// writing PNGs +// ---------------------------------------------------------------------------- + bool wxPNGHandler::SaveFile( wxImage *image, wxOutputStream& stream, bool verbose ) { wxPNGInfoStruct wxinfo; @@ -428,16 +667,6 @@ bool wxPNGHandler::SaveFile( wxImage *image, wxOutputStream& stream, bool verbos #pragma warning(default:4611) #endif /* VC++ */ -bool wxPNGHandler::DoCanRead( wxInputStream& stream ) -{ - unsigned char hdr[4]; - - if ( !stream.Read(hdr, WXSIZEOF(hdr)) ) - return FALSE; - - return memcmp(hdr, "\211PNG", WXSIZEOF(hdr)) == 0; -} - #endif // wxUSE_STREAMS #endif // wxUSE_LIBPNG