c_renderer.py 文件源码

def grey_blit(src, dst, blend_mode=MJBLEND_NORMAL):
    """
    This is for grey + alpha images
    """
    # http://stackoverflow.com/a/3375291/190597
    # http://stackoverflow.com/a/9166671/190597
    # blending with alpha http://stackoverflow.com/questions/1613600/direct3d-rendering-2d-images-with-multiply-blending-mode-and-alpha
    # blending modes from: http://www.linuxtopia.org/online_books/graphics_tools/gimp_advanced_guide/gimp_guide_node55.html
    dt = dst.dtype
    src = src.astype(n.single)
    dst = dst.astype(n.single)
    out = n.empty(src.shape, dtype='float')
    alpha = n.index_exp[:, :, 1]
    rgb = n.index_exp[:, :, 0]
    src_a = src[alpha] / 255.0
    dst_a = dst[alpha] / 255.0
    out[alpha] = src_a + dst_a * (1 - src_a)
    old_setting = n.seterr(invalid='ignore')
    src_pre = src[rgb] * src_a
    dst_pre = dst[rgb] * dst_a
    # blend:
    blendfuncs = {
        MJBLEND_NORMAL: lambda s, d, sa_: s + d * sa_,
        MJBLEND_ADD: lambda s, d, sa_: n.minimum(255, s + d),
        MJBLEND_SUB: lambda s, d, sa_: n.maximum(0, s - d),
        MJBLEND_MULT: lambda s, d, sa_: s * d * sa_ / 255.0,
        MJBLEND_MULTINV: lambda s, d, sa_: (255.0 - s) * d * sa_ / 255.0,
        MJBLEND_SCREEN: lambda s, d, sa_: 255 - (1.0 / 255.0) * (255.0 - s) * (255.0 - d * sa_),
        MJBLEND_DIVIDE: lambda s, d, sa_: n.minimum(255, d * sa_ * 256.0 / (s + 1.0)),
        MJBLEND_MIN: lambda s, d, sa_: n.minimum(d * sa_, s),
        MJBLEND_MAX: lambda s, d, sa_: n.maximum(d * sa_, s),
    }
    out[rgb] = blendfuncs[blend_mode](src_pre, dst_pre, (1 - src_a))
    out[rgb] /= out[alpha]
    n.seterr(**old_setting)
    out[alpha] *= 255
    n.clip(out, 0, 255)
    # astype('uint8') maps np.nan (and np.inf) to 0
    out = out.astype(dt)
    return out