jcgryext-neon.c (4441B)
1 /* 2 * jcgryext-neon.c - grayscale colorspace conversion (Arm Neon) 3 * 4 * Copyright (C) 2020, Arm Limited. All Rights Reserved. 5 * 6 * This software is provided 'as-is', without any express or implied 7 * warranty. In no event will the authors be held liable for any damages 8 * arising from the use of this software. 9 * 10 * Permission is granted to anyone to use this software for any purpose, 11 * including commercial applications, and to alter it and redistribute it 12 * freely, subject to the following restrictions: 13 * 14 * 1. The origin of this software must not be misrepresented; you must not 15 * claim that you wrote the original software. If you use this software 16 * in a product, an acknowledgment in the product documentation would be 17 * appreciated but is not required. 18 * 2. Altered source versions must be plainly marked as such, and must not be 19 * misrepresented as being the original software. 20 * 3. This notice may not be removed or altered from any source distribution. 21 */ 22 23 /* This file is included by jcgray-neon.c */ 24 25 26 /* RGB -> Grayscale conversion is defined by the following equation: 27 * Y = 0.29900 * R + 0.58700 * G + 0.11400 * B 28 * 29 * Avoid floating point arithmetic by using shifted integer constants: 30 * 0.29899597 = 19595 * 2^-16 31 * 0.58700561 = 38470 * 2^-16 32 * 0.11399841 = 7471 * 2^-16 33 * These constants are defined in jcgray-neon.c 34 * 35 * This is the same computation as the RGB -> Y portion of RGB -> YCbCr. 36 */ 37 38 void jsimd_rgb_gray_convert_neon(JDIMENSION image_width, JSAMPARRAY input_buf, 39 JSAMPIMAGE output_buf, JDIMENSION output_row, 40 int num_rows) 41 { 42 JSAMPROW inptr; 43 JSAMPROW outptr; 44 /* Allocate temporary buffer for final (image_width % 16) pixels in row. */ 45 ALIGN(16) uint8_t tmp_buf[16 * RGB_PIXELSIZE]; 46 47 while (--num_rows >= 0) { 48 inptr = *input_buf++; 49 outptr = output_buf[0][output_row]; 50 output_row++; 51 52 int cols_remaining = image_width; 53 for (; cols_remaining > 0; cols_remaining -= 16) { 54 55 /* To prevent buffer overread by the vector load instructions, the last 56 * (image_width % 16) columns of data are first memcopied to a temporary 57 * buffer large enough to accommodate the vector load. 58 */ 59 if (cols_remaining < 16) { 60 memcpy(tmp_buf, inptr, cols_remaining * RGB_PIXELSIZE); 61 inptr = tmp_buf; 62 } 63 64 #if RGB_PIXELSIZE == 4 65 uint8x16x4_t input_pixels = vld4q_u8(inptr); 66 #else 67 uint8x16x3_t input_pixels = vld3q_u8(inptr); 68 #endif 69 uint16x8_t r_l = vmovl_u8(vget_low_u8(input_pixels.val[RGB_RED])); 70 uint16x8_t r_h = vmovl_u8(vget_high_u8(input_pixels.val[RGB_RED])); 71 uint16x8_t g_l = vmovl_u8(vget_low_u8(input_pixels.val[RGB_GREEN])); 72 uint16x8_t g_h = vmovl_u8(vget_high_u8(input_pixels.val[RGB_GREEN])); 73 uint16x8_t b_l = vmovl_u8(vget_low_u8(input_pixels.val[RGB_BLUE])); 74 uint16x8_t b_h = vmovl_u8(vget_high_u8(input_pixels.val[RGB_BLUE])); 75 76 /* Compute Y = 0.29900 * R + 0.58700 * G + 0.11400 * B */ 77 uint32x4_t y_ll = vmull_n_u16(vget_low_u16(r_l), F_0_298); 78 uint32x4_t y_lh = vmull_n_u16(vget_high_u16(r_l), F_0_298); 79 uint32x4_t y_hl = vmull_n_u16(vget_low_u16(r_h), F_0_298); 80 uint32x4_t y_hh = vmull_n_u16(vget_high_u16(r_h), F_0_298); 81 y_ll = vmlal_n_u16(y_ll, vget_low_u16(g_l), F_0_587); 82 y_lh = vmlal_n_u16(y_lh, vget_high_u16(g_l), F_0_587); 83 y_hl = vmlal_n_u16(y_hl, vget_low_u16(g_h), F_0_587); 84 y_hh = vmlal_n_u16(y_hh, vget_high_u16(g_h), F_0_587); 85 y_ll = vmlal_n_u16(y_ll, vget_low_u16(b_l), F_0_113); 86 y_lh = vmlal_n_u16(y_lh, vget_high_u16(b_l), F_0_113); 87 y_hl = vmlal_n_u16(y_hl, vget_low_u16(b_h), F_0_113); 88 y_hh = vmlal_n_u16(y_hh, vget_high_u16(b_h), F_0_113); 89 90 /* Descale Y values (rounding right shift) and narrow to 16-bit. */ 91 uint16x8_t y_l = vcombine_u16(vrshrn_n_u32(y_ll, 16), 92 vrshrn_n_u32(y_lh, 16)); 93 uint16x8_t y_h = vcombine_u16(vrshrn_n_u32(y_hl, 16), 94 vrshrn_n_u32(y_hh, 16)); 95 96 /* Narrow Y values to 8-bit and store to memory. Buffer overwrite is 97 * permitted up to the next multiple of ALIGN_SIZE bytes. 98 */ 99 vst1q_u8(outptr, vcombine_u8(vmovn_u16(y_l), vmovn_u16(y_h))); 100 101 /* Increment pointers. */ 102 inptr += (16 * RGB_PIXELSIZE); 103 outptr += 16; 104 } 105 } 106 }