kc3-lang/libjpeg-turbo/simd/arm/jdsample-neon.c

Branch - branch -main

• Show log

  Commit

• Hash : 4e151a4a
  Author :
  Date : 2025-08-26T21:11:07
  

  Remove vestigial filenames from SIMD code headers
  
  These were a relic of libjpeg/SIMD, which attempted to follow the
  conventions of the libjpeg source code, but they are no longer relevant
  (or even accurate in some cases.)
  

Download

• simd/arm/jdsample-neon.c

• /*
   * Upsampling (Arm Neon)
   *
   * Copyright (C) 2020, Arm Limited.  All Rights Reserved.
   * Copyright (C) 2020, 2024, D. R. Commander.  All Rights Reserved.
   *
   * This software is provided 'as-is', without any express or implied
   * warranty.  In no event will the authors be held liable for any damages
   * arising from the use of this software.
   *
   * Permission is granted to anyone to use this software for any purpose,
   * including commercial applications, and to alter it and redistribute it
   * freely, subject to the following restrictions:
   *
   * 1. The origin of this software must not be misrepresented; you must not
   *    claim that you wrote the original software. If you use this software
   *    in a product, an acknowledgment in the product documentation would be
   *    appreciated but is not required.
   * 2. Altered source versions must be plainly marked as such, and must not be
   *    misrepresented as being the original software.
   * 3. This notice may not be removed or altered from any source distribution.
   */
  
  #define JPEG_INTERNALS
  #include "../../src/jinclude.h"
  #include "../../src/jpeglib.h"
  #include "../../src/jsimd.h"
  #include "../../src/jdct.h"
  #include "../../src/jsimddct.h"
  #include "../jsimd.h"
  #include "neon-compat.h"
  
  #include <arm_neon.h>
  
  
  /* The diagram below shows a row of samples produced by h2v1 downsampling.
   *
   *                s0        s1        s2
   *            +---------+---------+---------+
   *            |         |         |         |
   *            | p0   p1 | p2   p3 | p4   p5 |
   *            |         |         |         |
   *            +---------+---------+---------+
   *
   * Samples s0-s2 were created by averaging the original pixel component values
   * centered at positions p0-p5 above.  To approximate those original pixel
   * component values, we proportionally blend the adjacent samples in each row.
   *
   * An upsampled pixel component value is computed by blending the sample
   * containing the pixel center with the nearest neighboring sample, in the
   * ratio 3:1.  For example:
   *     p1(upsampled) = 3/4 * s0 + 1/4 * s1
   *     p2(upsampled) = 3/4 * s1 + 1/4 * s0
   * When computing the first and last pixel component values in the row, there
   * is no adjacent sample to blend, so:
   *     p0(upsampled) = s0
   *     p5(upsampled) = s2
   */
  
  void jsimd_h2v1_fancy_upsample_neon(int max_v_samp_factor,
                                      JDIMENSION downsampled_width,
                                      JSAMPARRAY input_data,
                                      JSAMPARRAY *output_data_ptr)
  {
    JSAMPARRAY output_data = *output_data_ptr;
    JSAMPROW inptr, outptr;
    int inrow;
    unsigned colctr;
    /* Set up constants. */
    const uint16x8_t one_u16 = vdupq_n_u16(1);
    const uint8x8_t three_u8 = vdup_n_u8(3);
  
    for (inrow = 0; inrow < max_v_samp_factor; inrow++) {
      inptr = input_data[inrow];
      outptr = output_data[inrow];
      /* First pixel component value in this row of the original image */
      *outptr = (JSAMPLE)GETJSAMPLE(*inptr);
  
      /*    3/4 * containing sample + 1/4 * nearest neighboring sample
       * For p1: containing sample = s0, nearest neighboring sample = s1
       * For p2: containing sample = s1, nearest neighboring sample = s0
       */
      uint8x16_t s0 = vld1q_u8(inptr);
      uint8x16_t s1 = vld1q_u8(inptr + 1);
      /* Multiplication makes vectors twice as wide.  '_l' and '_h' suffixes
       * denote low half and high half respectively.
       */
      uint16x8_t s1_add_3s0_l =
        vmlal_u8(vmovl_u8(vget_low_u8(s1)), vget_low_u8(s0), three_u8);
      uint16x8_t s1_add_3s0_h =
        vmlal_u8(vmovl_u8(vget_high_u8(s1)), vget_high_u8(s0), three_u8);
      uint16x8_t s0_add_3s1_l =
        vmlal_u8(vmovl_u8(vget_low_u8(s0)), vget_low_u8(s1), three_u8);
      uint16x8_t s0_add_3s1_h =
        vmlal_u8(vmovl_u8(vget_high_u8(s0)), vget_high_u8(s1), three_u8);
      /* Add ordered dithering bias to odd pixel values. */
      s0_add_3s1_l = vaddq_u16(s0_add_3s1_l, one_u16);
      s0_add_3s1_h = vaddq_u16(s0_add_3s1_h, one_u16);
  
      /* The offset is initially 1, because the first pixel component has already
       * been stored.  However, in subsequent iterations of the SIMD loop, this
       * offset is (2 * colctr - 1) to stay within the bounds of the sample
       * buffers without having to resort to a slow scalar tail case for the last
       * (downsampled_width % 16) samples.  See "Creation of 2-D sample arrays"
       * in jmemmgr.c for more details.
       */
      unsigned outptr_offset = 1;
      uint8x16x2_t output_pixels;
  
      /* We use software pipelining to maximise performance.  The code indented
       * an extra two spaces begins the next iteration of the loop.
       */
      for (colctr = 16; colctr < downsampled_width; colctr += 16) {
  
          s0 = vld1q_u8(inptr + colctr - 1);
          s1 = vld1q_u8(inptr + colctr);
  
        /* Right-shift by 2 (divide by 4), narrow to 8-bit, and combine. */
        output_pixels.val[0] = vcombine_u8(vrshrn_n_u16(s1_add_3s0_l, 2),
                                           vrshrn_n_u16(s1_add_3s0_h, 2));
        output_pixels.val[1] = vcombine_u8(vshrn_n_u16(s0_add_3s1_l, 2),
                                           vshrn_n_u16(s0_add_3s1_h, 2));
  
          /* Multiplication makes vectors twice as wide.  '_l' and '_h' suffixes
           * denote low half and high half respectively.
           */
          s1_add_3s0_l =
            vmlal_u8(vmovl_u8(vget_low_u8(s1)), vget_low_u8(s0), three_u8);
          s1_add_3s0_h =
            vmlal_u8(vmovl_u8(vget_high_u8(s1)), vget_high_u8(s0), three_u8);
          s0_add_3s1_l =
            vmlal_u8(vmovl_u8(vget_low_u8(s0)), vget_low_u8(s1), three_u8);
          s0_add_3s1_h =
            vmlal_u8(vmovl_u8(vget_high_u8(s0)), vget_high_u8(s1), three_u8);
          /* Add ordered dithering bias to odd pixel values. */
          s0_add_3s1_l = vaddq_u16(s0_add_3s1_l, one_u16);
          s0_add_3s1_h = vaddq_u16(s0_add_3s1_h, one_u16);
  
        /* Store pixel component values to memory. */
        vst2q_u8(outptr + outptr_offset, output_pixels);
        outptr_offset = 2 * colctr - 1;
      }
  
      /* Complete the last iteration of the loop. */
  
      /* Right-shift by 2 (divide by 4), narrow to 8-bit, and combine. */
      output_pixels.val[0] = vcombine_u8(vrshrn_n_u16(s1_add_3s0_l, 2),
                                         vrshrn_n_u16(s1_add_3s0_h, 2));
      output_pixels.val[1] = vcombine_u8(vshrn_n_u16(s0_add_3s1_l, 2),
                                         vshrn_n_u16(s0_add_3s1_h, 2));
      /* Store pixel component values to memory. */
      vst2q_u8(outptr + outptr_offset, output_pixels);
  
      /* Last pixel component value in this row of the original image */
      outptr[2 * downsampled_width - 1] =
        GETJSAMPLE(inptr[downsampled_width - 1]);
    }
  }
  
  
  /* The diagram below shows an array of samples produced by h2v2 downsampling.
   *
   *                s0        s1        s2
   *            +---------+---------+---------+
   *            | p0   p1 | p2   p3 | p4   p5 |
   *       sA   |         |         |         |
   *            | p6   p7 | p8   p9 | p10  p11|
   *            +---------+---------+---------+
   *            | p12  p13| p14  p15| p16  p17|
   *       sB   |         |         |         |
   *            | p18  p19| p20  p21| p22  p23|
   *            +---------+---------+---------+
   *            | p24  p25| p26  p27| p28  p29|
   *       sC   |         |         |         |
   *            | p30  p31| p32  p33| p34  p35|
   *            +---------+---------+---------+
   *
   * Samples s0A-s2C were created by averaging the original pixel component
   * values centered at positions p0-p35 above.  To approximate one of those
   * original pixel component values, we proportionally blend the sample
   * containing the pixel center with the nearest neighboring samples in each
   * row, column, and diagonal.
   *
   * An upsampled pixel component value is computed by first blending the sample
   * containing the pixel center with the nearest neighboring samples in the
   * same column, in the ratio 3:1, and then blending each column sum with the
   * nearest neighboring column sum, in the ratio 3:1.  For example:
   *     p14(upsampled) = 3/4 * (3/4 * s1B + 1/4 * s1A) +
   *                      1/4 * (3/4 * s0B + 1/4 * s0A)
   *                    = 9/16 * s1B + 3/16 * s1A + 3/16 * s0B + 1/16 * s0A
   * When computing the first and last pixel component values in the row, there
   * is no horizontally adjacent sample to blend, so:
   *     p12(upsampled) = 3/4 * s0B + 1/4 * s0A
   *     p23(upsampled) = 3/4 * s2B + 1/4 * s2C
   * When computing the first and last pixel component values in the column,
   * there is no vertically adjacent sample to blend, so:
   *     p2(upsampled) = 3/4 * s1A + 1/4 * s0A
   *     p33(upsampled) = 3/4 * s1C + 1/4 * s2C
   * When computing the corner pixel component values, there is no adjacent
   * sample to blend, so:
   *     p0(upsampled) = s0A
   *     p35(upsampled) = s2C
   */
  
  void jsimd_h2v2_fancy_upsample_neon(int max_v_samp_factor,
                                      JDIMENSION downsampled_width,
                                      JSAMPARRAY input_data,
                                      JSAMPARRAY *output_data_ptr)
  {
    JSAMPARRAY output_data = *output_data_ptr;
    JSAMPROW inptr0, inptr1, inptr2, outptr0, outptr1;
    int inrow, outrow;
    unsigned colctr;
    /* Set up constants. */
    const uint16x8_t seven_u16 = vdupq_n_u16(7);
    const uint8x8_t three_u8 = vdup_n_u8(3);
    const uint16x8_t three_u16 = vdupq_n_u16(3);
  
    inrow = outrow = 0;
    while (outrow < max_v_samp_factor) {
      inptr0 = input_data[inrow - 1];
      inptr1 = input_data[inrow];
      inptr2 = input_data[inrow + 1];
      /* Suffixes 0 and 1 denote the upper and lower rows of output pixels,
       * respectively.
       */
      outptr0 = output_data[outrow++];
      outptr1 = output_data[outrow++];
  
      /* First pixel component value in this row of the original image */
      int s0colsum0 = GETJSAMPLE(*inptr1) * 3 + GETJSAMPLE(*inptr0);
      *outptr0 = (JSAMPLE)((s0colsum0 * 4 + 8) >> 4);
      int s0colsum1 = GETJSAMPLE(*inptr1) * 3 + GETJSAMPLE(*inptr2);
      *outptr1 = (JSAMPLE)((s0colsum1 * 4 + 8) >> 4);
  
      /* Step 1: Blend samples vertically in columns s0 and s1.
       * Leave the divide by 4 until the end, when it can be done for both
       * dimensions at once, right-shifting by 4.
       */
  
      /* Load and compute s0colsum0 and s0colsum1. */
      uint8x16_t s0A = vld1q_u8(inptr0);
      uint8x16_t s0B = vld1q_u8(inptr1);
      uint8x16_t s0C = vld1q_u8(inptr2);
      /* Multiplication makes vectors twice as wide.  '_l' and '_h' suffixes
       * denote low half and high half respectively.
       */
      uint16x8_t s0colsum0_l = vmlal_u8(vmovl_u8(vget_low_u8(s0A)),
                                        vget_low_u8(s0B), three_u8);
      uint16x8_t s0colsum0_h = vmlal_u8(vmovl_u8(vget_high_u8(s0A)),
                                        vget_high_u8(s0B), three_u8);
      uint16x8_t s0colsum1_l = vmlal_u8(vmovl_u8(vget_low_u8(s0C)),
                                        vget_low_u8(s0B), three_u8);
      uint16x8_t s0colsum1_h = vmlal_u8(vmovl_u8(vget_high_u8(s0C)),
                                        vget_high_u8(s0B), three_u8);
      /* Load and compute s1colsum0 and s1colsum1. */
      uint8x16_t s1A = vld1q_u8(inptr0 + 1);
      uint8x16_t s1B = vld1q_u8(inptr1 + 1);
      uint8x16_t s1C = vld1q_u8(inptr2 + 1);
      uint16x8_t s1colsum0_l = vmlal_u8(vmovl_u8(vget_low_u8(s1A)),
                                        vget_low_u8(s1B), three_u8);
      uint16x8_t s1colsum0_h = vmlal_u8(vmovl_u8(vget_high_u8(s1A)),
                                        vget_high_u8(s1B), three_u8);
      uint16x8_t s1colsum1_l = vmlal_u8(vmovl_u8(vget_low_u8(s1C)),
                                        vget_low_u8(s1B), three_u8);
      uint16x8_t s1colsum1_h = vmlal_u8(vmovl_u8(vget_high_u8(s1C)),
                                        vget_high_u8(s1B), three_u8);
  
      /* Step 2: Blend the already-blended columns. */
  
      uint16x8_t output0_p1_l = vmlaq_u16(s1colsum0_l, s0colsum0_l, three_u16);
      uint16x8_t output0_p1_h = vmlaq_u16(s1colsum0_h, s0colsum0_h, three_u16);
      uint16x8_t output0_p2_l = vmlaq_u16(s0colsum0_l, s1colsum0_l, three_u16);
      uint16x8_t output0_p2_h = vmlaq_u16(s0colsum0_h, s1colsum0_h, three_u16);
      uint16x8_t output1_p1_l = vmlaq_u16(s1colsum1_l, s0colsum1_l, three_u16);
      uint16x8_t output1_p1_h = vmlaq_u16(s1colsum1_h, s0colsum1_h, three_u16);
      uint16x8_t output1_p2_l = vmlaq_u16(s0colsum1_l, s1colsum1_l, three_u16);
      uint16x8_t output1_p2_h = vmlaq_u16(s0colsum1_h, s1colsum1_h, three_u16);
      /* Add ordered dithering bias to odd pixel values. */
      output0_p1_l = vaddq_u16(output0_p1_l, seven_u16);
      output0_p1_h = vaddq_u16(output0_p1_h, seven_u16);
      output1_p1_l = vaddq_u16(output1_p1_l, seven_u16);
      output1_p1_h = vaddq_u16(output1_p1_h, seven_u16);
      /* Right-shift by 4 (divide by 16), narrow to 8-bit, and combine. */
      uint8x16x2_t output_pixels0 = { {
        vcombine_u8(vshrn_n_u16(output0_p1_l, 4), vshrn_n_u16(output0_p1_h, 4)),
        vcombine_u8(vrshrn_n_u16(output0_p2_l, 4), vrshrn_n_u16(output0_p2_h, 4))
      } };
      uint8x16x2_t output_pixels1 = { {
        vcombine_u8(vshrn_n_u16(output1_p1_l, 4), vshrn_n_u16(output1_p1_h, 4)),
        vcombine_u8(vrshrn_n_u16(output1_p2_l, 4), vrshrn_n_u16(output1_p2_h, 4))
      } };
  
      /* Store pixel component values to memory.
       * The minimum size of the output buffer for each row is 64 bytes => no
       * need to worry about buffer overflow here.  See "Creation of 2-D sample
       * arrays" in jmemmgr.c for more details.
       */
      vst2q_u8(outptr0 + 1, output_pixels0);
      vst2q_u8(outptr1 + 1, output_pixels1);
  
      /* The first pixel of the image shifted our loads and stores by one byte.
       * We have to re-align on a 32-byte boundary at some point before the end
       * of the row (we do it now on the 32/33 pixel boundary) to stay within the
       * bounds of the sample buffers without having to resort to a slow scalar
       * tail case for the last (downsampled_width % 16) samples.  See "Creation
       * of 2-D sample arrays" in jmemmgr.c for more details.
       */
      for (colctr = 16; colctr < downsampled_width; colctr += 16) {
        /* Step 1: Blend samples vertically in columns s0 and s1. */
  
        /* Load and compute s0colsum0 and s0colsum1. */
        s0A = vld1q_u8(inptr0 + colctr - 1);
        s0B = vld1q_u8(inptr1 + colctr - 1);
        s0C = vld1q_u8(inptr2 + colctr - 1);
        s0colsum0_l = vmlal_u8(vmovl_u8(vget_low_u8(s0A)), vget_low_u8(s0B),
                               three_u8);
        s0colsum0_h = vmlal_u8(vmovl_u8(vget_high_u8(s0A)), vget_high_u8(s0B),
                               three_u8);
        s0colsum1_l = vmlal_u8(vmovl_u8(vget_low_u8(s0C)), vget_low_u8(s0B),
                               three_u8);
        s0colsum1_h = vmlal_u8(vmovl_u8(vget_high_u8(s0C)), vget_high_u8(s0B),
                               three_u8);
        /* Load and compute s1colsum0 and s1colsum1. */
        s1A = vld1q_u8(inptr0 + colctr);
        s1B = vld1q_u8(inptr1 + colctr);
        s1C = vld1q_u8(inptr2 + colctr);
        s1colsum0_l = vmlal_u8(vmovl_u8(vget_low_u8(s1A)), vget_low_u8(s1B),
                               three_u8);
        s1colsum0_h = vmlal_u8(vmovl_u8(vget_high_u8(s1A)), vget_high_u8(s1B),
                               three_u8);
        s1colsum1_l = vmlal_u8(vmovl_u8(vget_low_u8(s1C)), vget_low_u8(s1B),
                               three_u8);
        s1colsum1_h = vmlal_u8(vmovl_u8(vget_high_u8(s1C)), vget_high_u8(s1B),
                               three_u8);
  
        /* Step 2: Blend the already-blended columns. */
  
        output0_p1_l = vmlaq_u16(s1colsum0_l, s0colsum0_l, three_u16);
        output0_p1_h = vmlaq_u16(s1colsum0_h, s0colsum0_h, three_u16);
        output0_p2_l = vmlaq_u16(s0colsum0_l, s1colsum0_l, three_u16);
        output0_p2_h = vmlaq_u16(s0colsum0_h, s1colsum0_h, three_u16);
        output1_p1_l = vmlaq_u16(s1colsum1_l, s0colsum1_l, three_u16);
        output1_p1_h = vmlaq_u16(s1colsum1_h, s0colsum1_h, three_u16);
        output1_p2_l = vmlaq_u16(s0colsum1_l, s1colsum1_l, three_u16);
        output1_p2_h = vmlaq_u16(s0colsum1_h, s1colsum1_h, three_u16);
        /* Add ordered dithering bias to odd pixel values. */
        output0_p1_l = vaddq_u16(output0_p1_l, seven_u16);
        output0_p1_h = vaddq_u16(output0_p1_h, seven_u16);
        output1_p1_l = vaddq_u16(output1_p1_l, seven_u16);
        output1_p1_h = vaddq_u16(output1_p1_h, seven_u16);
        /* Right-shift by 4 (divide by 16), narrow to 8-bit, and combine. */
        output_pixels0.val[0] = vcombine_u8(vshrn_n_u16(output0_p1_l, 4),
                                            vshrn_n_u16(output0_p1_h, 4));
        output_pixels0.val[1] = vcombine_u8(vrshrn_n_u16(output0_p2_l, 4),
                                            vrshrn_n_u16(output0_p2_h, 4));
        output_pixels1.val[0] = vcombine_u8(vshrn_n_u16(output1_p1_l, 4),
                                            vshrn_n_u16(output1_p1_h, 4));
        output_pixels1.val[1] = vcombine_u8(vrshrn_n_u16(output1_p2_l, 4),
                                            vrshrn_n_u16(output1_p2_h, 4));
        /* Store pixel component values to memory. */
        vst2q_u8(outptr0 + 2 * colctr - 1, output_pixels0);
        vst2q_u8(outptr1 + 2 * colctr - 1, output_pixels1);
      }
  
      /* Last pixel component value in this row of the original image */
      int s1colsum0 = GETJSAMPLE(inptr1[downsampled_width - 1]) * 3 +
                      GETJSAMPLE(inptr0[downsampled_width - 1]);
      outptr0[2 * downsampled_width - 1] = (JSAMPLE)((s1colsum0 * 4 + 7) >> 4);
      int s1colsum1 = GETJSAMPLE(inptr1[downsampled_width - 1]) * 3 +
                      GETJSAMPLE(inptr2[downsampled_width - 1]);
      outptr1[2 * downsampled_width - 1] = (JSAMPLE)((s1colsum1 * 4 + 7) >> 4);
      inrow++;
    }
  }
  
  
  /* The diagram below shows a column of samples produced by h1v2 downsampling
   * (or by losslessly rotating or transposing an h2v1-downsampled image.)
   *
   *            +---------+
   *            |   p0    |
   *     sA     |         |
   *            |   p1    |
   *            +---------+
   *            |   p2    |
   *     sB     |         |
   *            |   p3    |
   *            +---------+
   *            |   p4    |
   *     sC     |         |
   *            |   p5    |
   *            +---------+
   *
   * Samples sA-sC were created by averaging the original pixel component values
   * centered at positions p0-p5 above.  To approximate those original pixel
   * component values, we proportionally blend the adjacent samples in each
   * column.
   *
   * An upsampled pixel component value is computed by blending the sample
   * containing the pixel center with the nearest neighboring sample, in the
   * ratio 3:1.  For example:
   *     p1(upsampled) = 3/4 * sA + 1/4 * sB
   *     p2(upsampled) = 3/4 * sB + 1/4 * sA
   * When computing the first and last pixel component values in the column,
   * there is no adjacent sample to blend, so:
   *     p0(upsampled) = sA
   *     p5(upsampled) = sC
   */
  
  void jsimd_h1v2_fancy_upsample_neon(int max_v_samp_factor,
                                      JDIMENSION downsampled_width,
                                      JSAMPARRAY input_data,
                                      JSAMPARRAY *output_data_ptr)
  {
    JSAMPARRAY output_data = *output_data_ptr;
    JSAMPROW inptr0, inptr1, inptr2, outptr0, outptr1;
    int inrow, outrow;
    unsigned colctr;
    /* Set up constants. */
    const uint16x8_t one_u16 = vdupq_n_u16(1);
    const uint8x8_t three_u8 = vdup_n_u8(3);
  
    inrow = outrow = 0;
    while (outrow < max_v_samp_factor) {
      inptr0 = input_data[inrow - 1];
      inptr1 = input_data[inrow];
      inptr2 = input_data[inrow + 1];
      /* Suffixes 0 and 1 denote the upper and lower rows of output pixels,
       * respectively.
       */
      outptr0 = output_data[outrow++];
      outptr1 = output_data[outrow++];
      inrow++;
  
      /* The size of the input and output buffers is always a multiple of 32
       * bytes => no need to worry about buffer overflow when reading/writing
       * memory.  See "Creation of 2-D sample arrays" in jmemmgr.c for more
       * details.
       */
      for (colctr = 0; colctr < downsampled_width; colctr += 16) {
        /* Load samples. */
        uint8x16_t sA = vld1q_u8(inptr0 + colctr);
        uint8x16_t sB = vld1q_u8(inptr1 + colctr);
        uint8x16_t sC = vld1q_u8(inptr2 + colctr);
        /* Blend samples vertically. */
        uint16x8_t colsum0_l = vmlal_u8(vmovl_u8(vget_low_u8(sA)),
                                        vget_low_u8(sB), three_u8);
        uint16x8_t colsum0_h = vmlal_u8(vmovl_u8(vget_high_u8(sA)),
                                        vget_high_u8(sB), three_u8);
        uint16x8_t colsum1_l = vmlal_u8(vmovl_u8(vget_low_u8(sC)),
                                        vget_low_u8(sB), three_u8);
        uint16x8_t colsum1_h = vmlal_u8(vmovl_u8(vget_high_u8(sC)),
                                        vget_high_u8(sB), three_u8);
        /* Add ordered dithering bias to pixel values in even output rows. */
        colsum0_l = vaddq_u16(colsum0_l, one_u16);
        colsum0_h = vaddq_u16(colsum0_h, one_u16);
        /* Right-shift by 2 (divide by 4), narrow to 8-bit, and combine. */
        uint8x16_t output_pixels0 = vcombine_u8(vshrn_n_u16(colsum0_l, 2),
                                                vshrn_n_u16(colsum0_h, 2));
        uint8x16_t output_pixels1 = vcombine_u8(vrshrn_n_u16(colsum1_l, 2),
                                                vrshrn_n_u16(colsum1_h, 2));
        /* Store pixel component values to memory. */
        vst1q_u8(outptr0 + colctr, output_pixels0);
        vst1q_u8(outptr1 + colctr, output_pixels1);
      }
    }
  }
  
  
  /* The diagram below shows a row of samples produced by h2v1 downsampling.
   *
   *                s0        s1
   *            +---------+---------+
   *            |         |         |
   *            | p0   p1 | p2   p3 |
   *            |         |         |
   *            +---------+---------+
   *
   * Samples s0 and s1 were created by averaging the original pixel component
   * values centered at positions p0-p3 above.  To approximate those original
   * pixel component values, we duplicate the samples horizontally:
   *     p0(upsampled) = p1(upsampled) = s0
   *     p2(upsampled) = p3(upsampled) = s1
   */
  
  void jsimd_h2v1_upsample_neon(int max_v_samp_factor, JDIMENSION output_width,
                                JSAMPARRAY input_data,
                                JSAMPARRAY *output_data_ptr)
  {
    JSAMPARRAY output_data = *output_data_ptr;
    JSAMPROW inptr, outptr;
    int inrow;
    unsigned colctr;
  
    for (inrow = 0; inrow < max_v_samp_factor; inrow++) {
      inptr = input_data[inrow];
      outptr = output_data[inrow];
      for (colctr = 0; 2 * colctr < output_width; colctr += 16) {
        uint8x16_t samples = vld1q_u8(inptr + colctr);
        /* Duplicate the samples.  The store operation below interleaves them so
         * that adjacent pixel component values take on the same sample value,
         * per above.
         */
        uint8x16x2_t output_pixels = { { samples, samples } };
        /* Store pixel component values to memory.
         * Due to the way sample buffers are allocated, we don't need to worry
         * about tail cases when output_width is not a multiple of 32.  See
         * "Creation of 2-D sample arrays" in jmemmgr.c for details.
         */
        vst2q_u8(outptr + 2 * colctr, output_pixels);
      }
    }
  }
  
  
  /* The diagram below shows an array of samples produced by h2v2 downsampling.
   *
   *                s0        s1
   *            +---------+---------+
   *            | p0   p1 | p2   p3 |
   *       sA   |         |         |
   *            | p4   p5 | p6   p7 |
   *            +---------+---------+
   *            | p8   p9 | p10  p11|
   *       sB   |         |         |
   *            | p12  p13| p14  p15|
   *            +---------+---------+
   *
   * Samples s0A-s1B were created by averaging the original pixel component
   * values centered at positions p0-p15 above.  To approximate those original
   * pixel component values, we duplicate the samples both horizontally and
   * vertically:
   *     p0(upsampled) = p1(upsampled) = p4(upsampled) = p5(upsampled) = s0A
   *     p2(upsampled) = p3(upsampled) = p6(upsampled) = p7(upsampled) = s1A
   *     p8(upsampled) = p9(upsampled) = p12(upsampled) = p13(upsampled) = s0B
   *     p10(upsampled) = p11(upsampled) = p14(upsampled) = p15(upsampled) = s1B
   */
  
  void jsimd_h2v2_upsample_neon(int max_v_samp_factor, JDIMENSION output_width,
                                JSAMPARRAY input_data,
                                JSAMPARRAY *output_data_ptr)
  {
    JSAMPARRAY output_data = *output_data_ptr;
    JSAMPROW inptr, outptr0, outptr1;
    int inrow, outrow;
    unsigned colctr;
  
    for (inrow = 0, outrow = 0; outrow < max_v_samp_factor; inrow++) {
      inptr = input_data[inrow];
      outptr0 = output_data[outrow++];
      outptr1 = output_data[outrow++];
  
      for (colctr = 0; 2 * colctr < output_width; colctr += 16) {
        uint8x16_t samples = vld1q_u8(inptr + colctr);
        /* Duplicate the samples.  The store operation below interleaves them so
         * that adjacent pixel component values take on the same sample value,
         * per above.
         */
        uint8x16x2_t output_pixels = { { samples, samples } };
        /* Store pixel component values for both output rows to memory.
         * Due to the way sample buffers are allocated, we don't need to worry
         * about tail cases when output_width is not a multiple of 32.  See
         * "Creation of 2-D sample arrays" in jmemmgr.c for details.
         */
        vst2q_u8(outptr0 + 2 * colctr, output_pixels);
        vst2q_u8(outptr1 + 2 * colctr, output_pixels);
      }
    }
  }
  

Download