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149 lines
6.4 KiB
149 lines
6.4 KiB
4 months ago
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/*
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* jccolext-neon.c - colorspace conversion (32-bit Arm Neon)
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*
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* Copyright (C) 2020, Arm Limited. All Rights Reserved.
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* Copyright (C) 2020, D. R. Commander. All Rights Reserved.
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*
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* This software is provided 'as-is', without any express or implied
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* warranty. In no event will the authors be held liable for any damages
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* arising from the use of this software.
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*
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* Permission is granted to anyone to use this software for any purpose,
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* including commercial applications, and to alter it and redistribute it
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* freely, subject to the following restrictions:
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*
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* 1. The origin of this software must not be misrepresented; you must not
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* claim that you wrote the original software. If you use this software
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* in a product, an acknowledgment in the product documentation would be
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* appreciated but is not required.
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* 2. Altered source versions must be plainly marked as such, and must not be
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* misrepresented as being the original software.
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* 3. This notice may not be removed or altered from any source distribution.
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*/
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/* This file is included by jccolor-neon.c */
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/* RGB -> YCbCr conversion is defined by the following equations:
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* Y = 0.29900 * R + 0.58700 * G + 0.11400 * B
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* Cb = -0.16874 * R - 0.33126 * G + 0.50000 * B + 128
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* Cr = 0.50000 * R - 0.41869 * G - 0.08131 * B + 128
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*
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* Avoid floating point arithmetic by using shifted integer constants:
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* 0.29899597 = 19595 * 2^-16
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* 0.58700561 = 38470 * 2^-16
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* 0.11399841 = 7471 * 2^-16
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* 0.16874695 = 11059 * 2^-16
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* 0.33125305 = 21709 * 2^-16
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* 0.50000000 = 32768 * 2^-16
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* 0.41868592 = 27439 * 2^-16
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* 0.08131409 = 5329 * 2^-16
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* These constants are defined in jccolor-neon.c
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*
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* We add the fixed-point equivalent of 0.5 to Cb and Cr, which effectively
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* rounds up or down the result via integer truncation.
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*/
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void jsimd_rgb_ycc_convert_neon(JDIMENSION image_width, JSAMPARRAY input_buf,
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JSAMPIMAGE output_buf, JDIMENSION output_row,
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int num_rows)
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{
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/* Pointer to RGB(X/A) input data */
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JSAMPROW inptr;
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/* Pointers to Y, Cb, and Cr output data */
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JSAMPROW outptr0, outptr1, outptr2;
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/* Allocate temporary buffer for final (image_width % 8) pixels in row. */
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ALIGN(16) uint8_t tmp_buf[8 * RGB_PIXELSIZE];
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/* Set up conversion constants. */
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#ifdef HAVE_VLD1_U16_X2
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const uint16x4x2_t consts = vld1_u16_x2(jsimd_rgb_ycc_neon_consts);
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#else
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/* GCC does not currently support the intrinsic vld1_<type>_x2(). */
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const uint16x4_t consts1 = vld1_u16(jsimd_rgb_ycc_neon_consts);
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const uint16x4_t consts2 = vld1_u16(jsimd_rgb_ycc_neon_consts + 4);
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const uint16x4x2_t consts = { { consts1, consts2 } };
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#endif
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const uint32x4_t scaled_128_5 = vdupq_n_u32((128 << 16) + 32767);
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while (--num_rows >= 0) {
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inptr = *input_buf++;
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outptr0 = output_buf[0][output_row];
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outptr1 = output_buf[1][output_row];
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outptr2 = output_buf[2][output_row];
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output_row++;
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int cols_remaining = image_width;
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for (; cols_remaining > 0; cols_remaining -= 8) {
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/* To prevent buffer overread by the vector load instructions, the last
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* (image_width % 8) columns of data are first memcopied to a temporary
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* buffer large enough to accommodate the vector load.
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*/
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if (cols_remaining < 8) {
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memcpy(tmp_buf, inptr, cols_remaining * RGB_PIXELSIZE);
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inptr = tmp_buf;
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}
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#if RGB_PIXELSIZE == 4
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uint8x8x4_t input_pixels = vld4_u8(inptr);
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#else
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uint8x8x3_t input_pixels = vld3_u8(inptr);
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#endif
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uint16x8_t r = vmovl_u8(input_pixels.val[RGB_RED]);
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uint16x8_t g = vmovl_u8(input_pixels.val[RGB_GREEN]);
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uint16x8_t b = vmovl_u8(input_pixels.val[RGB_BLUE]);
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/* Compute Y = 0.29900 * R + 0.58700 * G + 0.11400 * B */
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uint32x4_t y_low = vmull_lane_u16(vget_low_u16(r), consts.val[0], 0);
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y_low = vmlal_lane_u16(y_low, vget_low_u16(g), consts.val[0], 1);
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y_low = vmlal_lane_u16(y_low, vget_low_u16(b), consts.val[0], 2);
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uint32x4_t y_high = vmull_lane_u16(vget_high_u16(r), consts.val[0], 0);
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y_high = vmlal_lane_u16(y_high, vget_high_u16(g), consts.val[0], 1);
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y_high = vmlal_lane_u16(y_high, vget_high_u16(b), consts.val[0], 2);
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/* Compute Cb = -0.16874 * R - 0.33126 * G + 0.50000 * B + 128 */
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uint32x4_t cb_low = scaled_128_5;
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cb_low = vmlsl_lane_u16(cb_low, vget_low_u16(r), consts.val[0], 3);
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cb_low = vmlsl_lane_u16(cb_low, vget_low_u16(g), consts.val[1], 0);
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cb_low = vmlal_lane_u16(cb_low, vget_low_u16(b), consts.val[1], 1);
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uint32x4_t cb_high = scaled_128_5;
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cb_high = vmlsl_lane_u16(cb_high, vget_high_u16(r), consts.val[0], 3);
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cb_high = vmlsl_lane_u16(cb_high, vget_high_u16(g), consts.val[1], 0);
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cb_high = vmlal_lane_u16(cb_high, vget_high_u16(b), consts.val[1], 1);
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/* Compute Cr = 0.50000 * R - 0.41869 * G - 0.08131 * B + 128 */
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uint32x4_t cr_low = scaled_128_5;
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cr_low = vmlal_lane_u16(cr_low, vget_low_u16(r), consts.val[1], 1);
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cr_low = vmlsl_lane_u16(cr_low, vget_low_u16(g), consts.val[1], 2);
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cr_low = vmlsl_lane_u16(cr_low, vget_low_u16(b), consts.val[1], 3);
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uint32x4_t cr_high = scaled_128_5;
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cr_high = vmlal_lane_u16(cr_high, vget_high_u16(r), consts.val[1], 1);
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cr_high = vmlsl_lane_u16(cr_high, vget_high_u16(g), consts.val[1], 2);
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cr_high = vmlsl_lane_u16(cr_high, vget_high_u16(b), consts.val[1], 3);
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/* Descale Y values (rounding right shift) and narrow to 16-bit. */
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uint16x8_t y_u16 = vcombine_u16(vrshrn_n_u32(y_low, 16),
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vrshrn_n_u32(y_high, 16));
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/* Descale Cb values (right shift) and narrow to 16-bit. */
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uint16x8_t cb_u16 = vcombine_u16(vshrn_n_u32(cb_low, 16),
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vshrn_n_u32(cb_high, 16));
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/* Descale Cr values (right shift) and narrow to 16-bit. */
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uint16x8_t cr_u16 = vcombine_u16(vshrn_n_u32(cr_low, 16),
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vshrn_n_u32(cr_high, 16));
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/* Narrow Y, Cb, and Cr values to 8-bit and store to memory. Buffer
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* overwrite is permitted up to the next multiple of ALIGN_SIZE bytes.
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*/
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vst1_u8(outptr0, vmovn_u16(y_u16));
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vst1_u8(outptr1, vmovn_u16(cb_u16));
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vst1_u8(outptr2, vmovn_u16(cr_u16));
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/* Increment pointers. */
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inptr += (8 * RGB_PIXELSIZE);
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outptr0 += 8;
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outptr1 += 8;
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outptr2 += 8;
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}
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}
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}
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