When Imlib2 draws an image onto another or an image onto a drawable it is able to do more than just blend the result on using the given alpha channel of the image. It is also able to do saturating additive, subtractive and a combination of the both (called reshade) rendering. The default mode is IMLIB_OP_COPY. you can also set it to IMLIB_OP_ADD, IMLIB_OP_SUBTRACT or IMLIB_OP_RESHADE. Use this function to set the rendering operation. IMLIB_OP_COPY performs basic alpha blending: DST = (SRC * A) + (DST * (1 - A)). IMLIB_OP_ADD does DST = DST + (SRC * A). IMLIB_OP_SUBTRACT does DST = DST - (SRC * A) and IMLIB_OP_RESHADE does DST = DST + (((SRC - 0.5) / 2) * A).
Definition at line 1116 of file imlib2.c.
ctx = imlib_context_new();
ctx->operation = operation;