Manual Pages for UNIX Operating System command usage for man mlib_ImageZoomTranslateBlend

mediaLib Library Functions    mlib_ImageZoomTranslateBlend(3MLIB)



NAME
     mlib_ImageZoomTranslateBlend  -  image  scaling  with  alpha
     blending

SYNOPSIS
     cc [ flag... ] file... -lmlib [ library... ]
     #include 

     mlib_status mlib_ImageZoomTranslateBlend(mlib_image *dst,
          const mlib_image *src, mlib_d64 zoomx, mlib_d64 zoomy,
          mlib_d64 tx, mlib_d64 ty, mlib_filter filter, mlib_edge edge,
          mlib_blend blend, mlib_s32 alpha, mlib_s32 cmask);


DESCRIPTION
     The mlib_ImageZoomTranslateBlend() function will enlarge  or
     minify  the  source  image by the X and Y zoom factors, with
     translation, and blend it with the destination image.


     It uses the following equation for coordinate mapping:

       xd = zoomx*xs + tx
       yd = zoomy*ys + ty



     where a point with coordinates (xs, ys) in the source  image
     is mapped to a point with coordinates (xd, yd) in the desti-
     nation image.


     The center of the upper-left corner pixel  of  an  image  is
     located at (0.5, 0.5).


     The alpha blending is closely combined with  the  interpola-
     tion  to achieve better performance.  Part of alpha blending
     has to be performed before or together with  the  interpola-
     tion if the source image has an alpha channel. In that case,
     the color components of each neighboring source pixel  which
     participates  in  the interpolation (src_r and etc.) have to
     be pre-multiplied by the alpha component of the same  source
     pixel  (src_a).   After the interpolation, the overall alpha
     (alpha), the interpolated source alpha  (interp_a)  and  the
     destination  pixel's original alpha (dst_a, if any) are used
     to blend the  interpolated  source  pixel  (with  components
     interp_r  and  etc.)  with  the destination pixel (with com-
     ponents dst_r and etc.).






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mediaLib Library Functions    mlib_ImageZoomTranslateBlend(3MLIB)



     The MLIB_BLEND_GTK_SRC blending is similar to the  SRC  rule
     of  the  Porter-Duff  rules  for  image  compositing.  It is
     defined by

       Cd = Cs
       Ad = As



     in general, and by the following formula for this function:

       if (interp_a != 0.0) {
            if (dst_has_alpha) {
                 dst_r = interp_r/interp_a;
                 dst_g = interp_g/interp_a;
                 dst_b = interp_b/interp_a;
                 dst_a = interp_a;
            } else {
                 dst_r = interp_r;
                 dst_g = interp_g;
                 dst_b = interp_b;
                 dst_a = 1.0; // implied
            }
       } else {
            dst_r = 0;
            dst_g = 0;
            dst_b = 0;
            dst_a = 0;
       }



     The  MLIB_BLEND_GTK_SRC_OVER   or   MLIB_BLEND_GTK_SRC_OVER2
     blending  is similar to the SRC_OVER rule of the Porter-Duff
     rules for image compositing.  It is defined by

       Cd = Cs + Cd*(1 - As)
       Ad = As + Ad*(1 - As)



     in general, and by the following formula for this function:

       w = alpha*interp_a + (1 - alpha*interp_a)*dst_a;
       if (w != 0.0) {
            dst_r = (alpha*interp_r +
                 (1 - alpha*interp_a)*dst_a*dst_r)/w;
            dst_g = (alpha*interp_g +
                 (1 - alpha*interp_a)*dst_a*dst_g)/w;
            dst_b = (alpha*interp_b +
                 (1 - alpha*interp_a)*dst_a*dst_b)/w;
            dst_a = w;



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mediaLib Library Functions    mlib_ImageZoomTranslateBlend(3MLIB)



       } else if (MLIB_BLEND_GTK_SRC_OVER) {
            dst_r = 0;
            dst_g = 0;
            dst_b = 0;
            dst_a = 0;
       }



     where alpha, src_a, interp_a and dst_a are assumed to be  in
     the range of [0.0, 1.0].


     For an image with 4 channels, the first or the fourth  chan-
     nel  is considered the alpha channel if cmask equals 8 or 1,
     respectively. An image with 3 channels is considered to have
     no  alpha  channel,  which  is equivalent to having an alpha
     channel filled with all 1.0, or 0xff in case  of  MLIB_BYTE,
     if the general formulas for blending shown above are used.


     Both src and dst must be of type MLIB_BYTE.  They  can  have
     either 3 or 4 channels.


     The src image cannot have width or height larger than 32767.

PARAMETERS
     The function takes the following arguments:

     dst       Pointer to destination image.


     src       Pointer to first source image.


     zoomx     X zoom factor. zoomx > 0.0.


     zoomy     Y zoom factor. zoomy > 0.0.


     tx        X translation.


     ty        Y translation.


     filter    Type of resampling filter. It can be  one  of  the
               following:

                 MLIB_NEAREST



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mediaLib Library Functions    mlib_ImageZoomTranslateBlend(3MLIB)



                 MLIB_BILINEAR
                 MLIB_BICUBIC
                 MLIB_BICUBIC2



     edge      Type of edge condition. It can be one of the  fol-
               lowing:

                 MLIB_EDGE_DST_NO_WRITE
                 MLIB_EDGE_DST_FILL_ZERO
                 MLIB_EDGE_OP_NEAREST
                 MLIB_EDGE_SRC_EXTEND
                 MLIB_EDGE_SRC_EXTEND_INDEF
                 MLIB_EDGE_SRC_PADDED



     blend     Type of alpha blending. It can be one of the  fol-
               lowing:

                 MLIB_BLEND_GTK_SRC
                 MLIB_BLEND_GTK_SRC_OVER
                 MLIB_BLEND_GTK_SRC_OVER2



     alpha     Overall alpha for blending.


     cmask     Channel mask to indicate the alpha channel.


RETURN VALUES
     The function returns MLIB_SUCCESS if  successful.  Otherwise
     it returns MLIB_FAILURE.

ATTRIBUTES
     See attributes(5) for descriptions of the  following  attri-
     butes:















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mediaLib Library Functions    mlib_ImageZoomTranslateBlend(3MLIB)



     ____________________________________________________________
    |       ATTRIBUTE TYPE        |       ATTRIBUTE VALUE       |
    |_____________________________|_____________________________|
    | Interface Stability         | Committed                   |
    |_____________________________|_____________________________|
    | MT-Level                    | MT-Safe                     |
    |_____________________________|_____________________________|


SEE ALSO
     mlib_ImageZoomBlend(3MLIB),
     mlib_ImageZoomTranslateTableBlend(3MLIB), attributes(5)











































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