| /* |
| * jcgryext-neon.c - grayscale colorspace conversion (Arm Neon) |
| * |
| * Copyright (C) 2020, Arm Limited. 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 jcgray-neon.c */ |
| |
| |
| /* RGB -> Grayscale conversion is defined by the following equation: |
| * Y = 0.29900 * R + 0.58700 * G + 0.11400 * B |
| * |
| * Avoid floating point arithmetic by using shifted integer constants: |
| * 0.29899597 = 19595 * 2^-16 |
| * 0.58700561 = 38470 * 2^-16 |
| * 0.11399841 = 7471 * 2^-16 |
| * These constants are defined in jcgray-neon.c |
| * |
| * This is the same computation as the RGB -> Y portion of RGB -> YCbCr. |
| */ |
| |
| void jsimd_rgb_gray_convert_neon(JDIMENSION image_width, JSAMPARRAY input_buf, |
| JSAMPIMAGE output_buf, JDIMENSION output_row, |
| int num_rows) |
| { |
| JSAMPROW inptr; |
| JSAMPROW outptr; |
| /* Allocate temporary buffer for final (image_width % 16) pixels in row. */ |
| ALIGN(16) uint8_t tmp_buf[16 * RGB_PIXELSIZE]; |
| |
| while (--num_rows >= 0) { |
| inptr = *input_buf++; |
| outptr = output_buf[0][output_row]; |
| output_row++; |
| |
| int cols_remaining = image_width; |
| for (; cols_remaining > 0; cols_remaining -= 16) { |
| |
| /* To prevent buffer overread by the vector load instructions, the last |
| * (image_width % 16) columns of data are first memcopied to a temporary |
| * buffer large enough to accommodate the vector load. |
| */ |
| if (cols_remaining < 16) { |
| memcpy(tmp_buf, inptr, cols_remaining * RGB_PIXELSIZE); |
| inptr = tmp_buf; |
| } |
| |
| #if RGB_PIXELSIZE == 4 |
| uint8x16x4_t input_pixels = vld4q_u8(inptr); |
| #else |
| uint8x16x3_t input_pixels = vld3q_u8(inptr); |
| #endif |
| uint16x8_t r_l = vmovl_u8(vget_low_u8(input_pixels.val[RGB_RED])); |
| uint16x8_t r_h = vmovl_u8(vget_high_u8(input_pixels.val[RGB_RED])); |
| uint16x8_t g_l = vmovl_u8(vget_low_u8(input_pixels.val[RGB_GREEN])); |
| uint16x8_t g_h = vmovl_u8(vget_high_u8(input_pixels.val[RGB_GREEN])); |
| uint16x8_t b_l = vmovl_u8(vget_low_u8(input_pixels.val[RGB_BLUE])); |
| uint16x8_t b_h = vmovl_u8(vget_high_u8(input_pixels.val[RGB_BLUE])); |
| |
| /* Compute Y = 0.29900 * R + 0.58700 * G + 0.11400 * B */ |
| uint32x4_t y_ll = vmull_n_u16(vget_low_u16(r_l), F_0_298); |
| uint32x4_t y_lh = vmull_n_u16(vget_high_u16(r_l), F_0_298); |
| uint32x4_t y_hl = vmull_n_u16(vget_low_u16(r_h), F_0_298); |
| uint32x4_t y_hh = vmull_n_u16(vget_high_u16(r_h), F_0_298); |
| y_ll = vmlal_n_u16(y_ll, vget_low_u16(g_l), F_0_587); |
| y_lh = vmlal_n_u16(y_lh, vget_high_u16(g_l), F_0_587); |
| y_hl = vmlal_n_u16(y_hl, vget_low_u16(g_h), F_0_587); |
| y_hh = vmlal_n_u16(y_hh, vget_high_u16(g_h), F_0_587); |
| y_ll = vmlal_n_u16(y_ll, vget_low_u16(b_l), F_0_113); |
| y_lh = vmlal_n_u16(y_lh, vget_high_u16(b_l), F_0_113); |
| y_hl = vmlal_n_u16(y_hl, vget_low_u16(b_h), F_0_113); |
| y_hh = vmlal_n_u16(y_hh, vget_high_u16(b_h), F_0_113); |
| |
| /* Descale Y values (rounding right shift) and narrow to 16-bit. */ |
| uint16x8_t y_l = vcombine_u16(vrshrn_n_u32(y_ll, 16), |
| vrshrn_n_u32(y_lh, 16)); |
| uint16x8_t y_h = vcombine_u16(vrshrn_n_u32(y_hl, 16), |
| vrshrn_n_u32(y_hh, 16)); |
| |
| /* Narrow Y values to 8-bit and store to memory. Buffer overwrite is |
| * permitted up to the next multiple of ALIGN_SIZE bytes. |
| */ |
| vst1q_u8(outptr, vcombine_u8(vmovn_u16(y_l), vmovn_u16(y_h))); |
| |
| /* Increment pointers. */ |
| inptr += (16 * RGB_PIXELSIZE); |
| outptr += 16; |
| } |
| } |
| } |
