mlib_ImageZoomTranslateTableBlend(3MLIB)		    mediaLib Library Functions			  mlib_ImageZoomTranslateTableBlend(3MLIB)

NAME

       mlib_ImageZoomTranslateTableBlend - image scaling using interpolation table, combined with alpha blending

SYNOPSIS

       cc [ flag... ] file... -lmlib [ library... ]
       #include <mlib.h>

       mlib_status mlib_ImageZoomTranslateTableBlend(mlib_image *dst, const mlib_image *src, mlib_d64 zoomx, mlib_d64 zoomy, mlib_d64 tx, mlib_d64
       ty, const void *table, mlib_edge edge, mlib_blend blend, mlib_s32 cmask);

DESCRIPTION

       The mlib_ImageZoomTranslateTableBlend() 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 destination image.

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

       It  is  assumed	that the overall alpha for controlling the blending between the source image and the destination image has been pre-multi-
       plied to the interpolation table for better performance.

       The alpha blending is closely combined with the interpolation to achieve better performance.  Part of alpha blending has  to  be  performed
       before or together with the interpolation 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 interpolated alpha (interp_a, which has been multiplied by the overall alpha because of the
       pre-multiplied interpolation table) 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 components dst_r and etc.).

       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 com-
       positing.  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 = interp_a + (1 - interp_a)*dst_a;
       if (w != 0.0) {
	    dst_r = (interp_r + (1 - interp_a)*dst_a*dst_r)/w;
	    dst_g = (interp_g + (1 - interp_a)*dst_a*dst_g)/w;
	    dst_b = (interp_b + (1 - interp_a)*dst_a*dst_b)/w;
	    dst_a = w;
       } else if (MLIB_BLEND_GTK_SRC_OVER) {
	    dst_r = 0;
	    dst_g = 0;
	    dst_b = 0;
	    dst_a = 0;
       }

       where 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 channel 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.

       table	       Pointer to interpolation table structure.

       edge	       Type of edge condition.	It can be one of the following:

		       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 following:

		       MLIB_BLEND_GTK_SRC
		       MLIB_BLEND_GTK_SRC_OVER
		       MLIB_BLEND_GTK_SRC_OVER2

       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 attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Evolving			   |
       +-----------------------------+-----------------------------+
       |MT-Level		     |MT-Safe			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       mlib_ImageZoomBlend(3MLIB), mlib_ImageZoomTranslateBlend(3MLIB), mlib_ImageInterpTableCreate(3MLIB), attributes(5)

SunOS 5.10							    10 Nov 2004 			  mlib_ImageZoomTranslateTableBlend(3MLIB)