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/*
* jccolext-neon.c - colorspace conversion (32-bit Arm Neon)
*
* Copyright (C) 2020, Arm Limited. All Rights Reserved.
* Copyright (C) 2020, 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.
*/
/* This file is included by jccolor-neon.c */
/* RGB -> YCbCr conversion is defined by the following equations:
* Y = 0.29900 * R + 0.58700 * G + 0.11400 * B
* Cb = -0.16874 * R - 0.33126 * G + 0.50000 * B + 128
* Cr = 0.50000 * R - 0.41869 * G - 0.08131 * B + 128
*
* Avoid floating point arithmetic by using shifted integer constants:
* 0.29899597 = 19595 * 2^-16
* 0.58700561 = 38470 * 2^-16
* 0.11399841 = 7471 * 2^-16
* 0.16874695 = 11059 * 2^-16
* 0.33125305 = 21709 * 2^-16
* 0.50000000 = 32768 * 2^-16
* 0.41868592 = 27439 * 2^-16
* 0.08131409 = 5329 * 2^-16
* These constants are defined in jccolor-neon.c
*
* We add the fixed-point equivalent of 0.5 to Cb and Cr, which effectively
* rounds up or down the result via integer truncation.
*/
void jsimd_rgb_ycc_convert_neon(JDIMENSION image_width, JSAMPARRAY input_buf,
JSAMPIMAGE output_buf, JDIMENSION output_row,
int num_rows)
{
/* Pointer to RGB(X/A) input data */
JSAMPROW inptr;
/* Pointers to Y, Cb, and Cr output data */
JSAMPROW outptr0, outptr1, outptr2;
/* Allocate temporary buffer for final (image_width % 8) pixels in row. */
ALIGN(16) uint8_t tmp_buf[8 * RGB_PIXELSIZE];
/* Set up conversion constants. */
#ifdef HAVE_VLD1_U16_X2
const uint16x4x2_t consts = vld1_u16_x2(jsimd_rgb_ycc_neon_consts);
#else
/* GCC does not currently support the intrinsic vld1_<type>_x2(). */
const uint16x4_t consts1 = vld1_u16(jsimd_rgb_ycc_neon_consts);
const uint16x4_t consts2 = vld1_u16(jsimd_rgb_ycc_neon_consts + 4);
const uint16x4x2_t consts = { { consts1, consts2 } };
#endif
const uint32x4_t scaled_128_5 = vdupq_n_u32((128 << 16) + 32767);
while (--num_rows >= 0) {
inptr = *input_buf++;
outptr0 = output_buf[0][output_row];
outptr1 = output_buf[1][output_row];
outptr2 = output_buf[2][output_row];
output_row++;
int cols_remaining = image_width;
for (; cols_remaining > 0; cols_remaining -= 8) {
/* To prevent buffer overread by the vector load instructions, the last
* (image_width % 8) columns of data are first memcopied to a temporary
* buffer large enough to accommodate the vector load.
*/
if (cols_remaining < 8) {
memcpy(tmp_buf, inptr, cols_remaining * RGB_PIXELSIZE);
inptr = tmp_buf;
}
#if RGB_PIXELSIZE == 4
uint8x8x4_t input_pixels = vld4_u8(inptr);
#else
uint8x8x3_t input_pixels = vld3_u8(inptr);
#endif
uint16x8_t r = vmovl_u8(input_pixels.val[RGB_RED]);
uint16x8_t g = vmovl_u8(input_pixels.val[RGB_GREEN]);
uint16x8_t b = vmovl_u8(input_pixels.val[RGB_BLUE]);
/* Compute Y = 0.29900 * R + 0.58700 * G + 0.11400 * B */
uint32x4_t y_low = vmull_lane_u16(vget_low_u16(r), consts.val[0], 0);
y_low = vmlal_lane_u16(y_low, vget_low_u16(g), consts.val[0], 1);
y_low = vmlal_lane_u16(y_low, vget_low_u16(b), consts.val[0], 2);
uint32x4_t y_high = vmull_lane_u16(vget_high_u16(r), consts.val[0], 0);
y_high = vmlal_lane_u16(y_high, vget_high_u16(g), consts.val[0], 1);
y_high = vmlal_lane_u16(y_high, vget_high_u16(b), consts.val[0], 2);
/* Compute Cb = -0.16874 * R - 0.33126 * G + 0.50000 * B + 128 */
uint32x4_t cb_low = scaled_128_5;
cb_low = vmlsl_lane_u16(cb_low, vget_low_u16(r), consts.val[0], 3);
cb_low = vmlsl_lane_u16(cb_low, vget_low_u16(g), consts.val[1], 0);
cb_low = vmlal_lane_u16(cb_low, vget_low_u16(b), consts.val[1], 1);
uint32x4_t cb_high = scaled_128_5;
cb_high = vmlsl_lane_u16(cb_high, vget_high_u16(r), consts.val[0], 3);
cb_high = vmlsl_lane_u16(cb_high, vget_high_u16(g), consts.val[1], 0);
cb_high = vmlal_lane_u16(cb_high, vget_high_u16(b), consts.val[1], 1);
/* Compute Cr = 0.50000 * R - 0.41869 * G - 0.08131 * B + 128 */
uint32x4_t cr_low = scaled_128_5;
cr_low = vmlal_lane_u16(cr_low, vget_low_u16(r), consts.val[1], 1);
cr_low = vmlsl_lane_u16(cr_low, vget_low_u16(g), consts.val[1], 2);
cr_low = vmlsl_lane_u16(cr_low, vget_low_u16(b), consts.val[1], 3);
uint32x4_t cr_high = scaled_128_5;
cr_high = vmlal_lane_u16(cr_high, vget_high_u16(r), consts.val[1], 1);
cr_high = vmlsl_lane_u16(cr_high, vget_high_u16(g), consts.val[1], 2);
cr_high = vmlsl_lane_u16(cr_high, vget_high_u16(b), consts.val[1], 3);
/* Descale Y values (rounding right shift) and narrow to 16-bit. */
uint16x8_t y_u16 = vcombine_u16(vrshrn_n_u32(y_low, 16),
vrshrn_n_u32(y_high, 16));
/* Descale Cb values (right shift) and narrow to 16-bit. */
uint16x8_t cb_u16 = vcombine_u16(vshrn_n_u32(cb_low, 16),
vshrn_n_u32(cb_high, 16));
/* Descale Cr values (right shift) and narrow to 16-bit. */
uint16x8_t cr_u16 = vcombine_u16(vshrn_n_u32(cr_low, 16),
vshrn_n_u32(cr_high, 16));
/* Narrow Y, Cb, and Cr values to 8-bit and store to memory. Buffer
* overwrite is permitted up to the next multiple of ALIGN_SIZE bytes.
*/
vst1_u8(outptr0, vmovn_u16(y_u16));
vst1_u8(outptr1, vmovn_u16(cb_u16));
vst1_u8(outptr2, vmovn_u16(cr_u16));
/* Increment pointers. */
inptr += (8 * RGB_PIXELSIZE);
outptr0 += 8;
outptr1 += 8;
outptr2 += 8;
}
}
}
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