16 bytes memory alignment for Mat images to be used with SSE instruction

asked 2015-10-28 05:29:02 -0500

updated 2015-10-28 07:31:01 -0500

Eduardo gravatar image

Hi every one,

I want to use the SSE instructions with Mat images in opencv, but the problem is that I need to perform memory alignment to 16 bytes (I am working with single chanel images).

I have a version which already works but with malloc and memcpy, but my purpose behind all of this is to remove the malloc and memcpy , since I am targeting embedded systems ,

here is my version

read the img_input (Mat) 
i_step : image step 
i_bpl  : image byte per line we need to get after alignment
 #ifdef __SSE__
       uint8_t *img = (uint8_t*)_mm_malloc(i_bpl*i_height*sizeof(uint8_t),16);
       #else
        uint8_t *img = (uint8_t*)malloc(i_bpl*i_height*sizeof(uint8_t));
  #endif
       memset (img,0,i_bpl*i_height*sizeof(uint8_t)); 
       if (i_bpl==i_step) {
       memcpy(img,m_img_L.data,i_bpl*i_height*sizeof(uint8_t));
       }
        else {
            for (int32_t v=0; v<i_height; v++) {
                memcpy(img+v*i_bpl,img_input.data+v*i_step,i_width*sizeof(uint8_t));
            }
        }

I want to 1. remove the dynamic allocation 2. do 16 bytes alignment for the image

Thanks in advance

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Comments

I don't think you could tell cv::imread to return a non-continuous mat with the appropriate padding value.

What you could do is to copy the first mat to another mat with the appropriate padding value (cv::Mat()). Then you could use directly the bitmap address for the SSE processing ?

A question: why targetting embedded systems require you to get rid off the malloc and memcpy ? At some point, these functions have to be used somewhere no ?

Eduardo gravatar imageEduardo ( 2015-10-28 10:53:35 -0500 )edit

if you need per row aligment look around MatAllocator

pklab gravatar imagepklab ( 2015-10-28 14:17:22 -0500 )edit