cc [ flag... ] file... lmlib [ library... ] #include <mlib.h> 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);
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 destination image.
The center of the upperleft corner pixel of an image is located at (0.5, 0.5).
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 premultiplied 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 components dst_r and etc.).
The MLIB_BLEND_GTK_SRC blending is similar to the SRC rule of the PorterDuff 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 PorterDuff 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; } 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 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.
The function takes the following arguments:
dst
src
zoomx
zoomy
tx
ty
filter
MLIB_NEAREST MLIB_BILINEAR MLIB_BICUBIC MLIB_BICUBIC2
edge
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
MLIB_BLEND_GTK_SRC MLIB_BLEND_GTK_SRC_OVER MLIB_BLEND_GTK_SRC_OVER2
alpha
cmask
The function returns MLIB_SUCCESS if successful. Otherwise it returns MLIB_FAILURE.
See attributes(5) for descriptions of the following attributes:

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