how to deinterleave image channel in SSE

问题:

is there any way we can DE-interleave 32bpp image channels similar as below code in neon.

//Read all r,g,b,a pixels into 4 registers
uint8x8x4_t SrcPixels8x8x4= vld4_u8(inPixel32);

ChannelR1_32x4 = vmovl_u16(vget_low_u16(vmovl_u8(SrcPixels8x8x4.val[0]))), 
channelR2_32x4 = vmovl_u16(vget_high_u16(vmovl_u8(SrcPixels8x8x4.val[0]))), vGaussElement_32x4_high);

basically i want all color channels in separate vectors with every vector has 4 elements of 32bits to do some calculation but i am not very familiar with SSE and could not find such instruction in SSE or if some one can provide better ways to do that? Any help is highly appreciated

回答1:

Since the 8 bit values are unsigned you can just do this with shifting and masking, much like you would for scalar code, e.g.

__m128i vrgba;

__m128i vr = _mm_and_si128(vrgba, _mm_set1_epi32(0xff));
__m128i vg = _mm_and_si128(_mm_srli_epi32(vrgba, 8), _mm_set1_epi32(0xff));
__m128i vb = _mm_and_si128(_mm_srli_epi32(vrgba, 16), _mm_set1_epi32(0xff));
__m128i va = _mm_srli_epi32(vrgba, 24);

Note that I'm assuming your RGBA elements have the R component in the LS 8 bits and the A component in the MS 8 bits, but if they are the opposite endianness you can just change the names of the vr/vg/vb/va vectors.