mediaLib Library Functions
mlib_ImageZoomTranslateTableBlend(3MLIB)
NAME
mlib_ImageZoomTranslateTableBlend - image scaling using
interpolation table, combined with alpha blendingSYNOPSIS
cc [ flag... ] file... -lmlib [ library... ]
#include
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 fac-
tors, 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 imageis 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). It is assumed that the overall alpha for controlling the blending between the source image and the destination imagehas been pre-multiplied to the interpolation table for
better performance.The alpha blending is closely combined with the interpola-
tion to achieve better performance. Part of alpha blendinghas 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 whichparticipates 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
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mediaLib Library Functionsmlib_ImageZoomTranslateTableBlend(3MLIB)
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 componentsinterp_r and etc.) with the destination pixel (with com-
ponents 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 compositing. It is defined byCd = Cs + Cd*(1 - As)
Ad = As + Ad*(1 - As)
in general, and by the following formula for this function:SunOS 5.11 Last change: 2 Mar 2007 2
mediaLib Library Functionsmlib_ImageZoomTranslateTableBlend(3MLIB)
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 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 alphachannel 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.SunOS 5.11 Last change: 2 Mar 2007 3
mediaLib Library Functionsmlib_ImageZoomTranslateTableBlend(3MLIB)
ty Y translation. table Pointer to interpolation table structure.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
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:SunOS 5.11 Last change: 2 Mar 2007 4
mediaLib Library Functionsmlib_ImageZoomTranslateTableBlend(3MLIB)
______________________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|_____________________________|_____________________________|
| Interface Stability | Committed ||_____________________________|_____________________________|
| MT-Level | MT-Safe |
|_____________________________|_____________________________|
SEE ALSO
mlib_ImageZoomBlend(3MLIB),
mlib_ImageZoomTranslateBlend(3MLIB),
mlib_ImageInterpTableCreate(3MLIB), attributes(5)
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mediaLib Library Functionsmlib_ImageZoomTranslateTableBlend(3MLIB)
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