mirror of https://github.com/axmolengine/axmol.git
107 lines
4.3 KiB
C
107 lines
4.3 KiB
C
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/*
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* jcgryext-neon.c - grayscale colorspace conversion (Arm Neon)
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*
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* Copyright (C) 2020, Arm Limited. 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 jcgray-neon.c */
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/* RGB -> Grayscale conversion is defined by the following equation:
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* Y = 0.29900 * R + 0.58700 * G + 0.11400 * B
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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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* These constants are defined in jcgray-neon.c
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*
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* This is the same computation as the RGB -> Y portion of RGB -> YCbCr.
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*/
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void jsimd_rgb_gray_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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JSAMPROW inptr;
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JSAMPROW outptr;
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/* Allocate temporary buffer for final (image_width % 16) pixels in row. */
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ALIGN(16) uint8_t tmp_buf[16 * RGB_PIXELSIZE];
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while (--num_rows >= 0) {
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inptr = *input_buf++;
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outptr = output_buf[0][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 -= 16) {
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/* To prevent buffer overread by the vector load instructions, the last
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* (image_width % 16) 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 < 16) {
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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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uint8x16x4_t input_pixels = vld4q_u8(inptr);
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#else
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uint8x16x3_t input_pixels = vld3q_u8(inptr);
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#endif
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uint16x8_t r_l = vmovl_u8(vget_low_u8(input_pixels.val[RGB_RED]));
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uint16x8_t r_h = vmovl_u8(vget_high_u8(input_pixels.val[RGB_RED]));
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uint16x8_t g_l = vmovl_u8(vget_low_u8(input_pixels.val[RGB_GREEN]));
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uint16x8_t g_h = vmovl_u8(vget_high_u8(input_pixels.val[RGB_GREEN]));
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uint16x8_t b_l = vmovl_u8(vget_low_u8(input_pixels.val[RGB_BLUE]));
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uint16x8_t b_h = vmovl_u8(vget_high_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_ll = vmull_n_u16(vget_low_u16(r_l), F_0_298);
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uint32x4_t y_lh = vmull_n_u16(vget_high_u16(r_l), F_0_298);
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uint32x4_t y_hl = vmull_n_u16(vget_low_u16(r_h), F_0_298);
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uint32x4_t y_hh = vmull_n_u16(vget_high_u16(r_h), F_0_298);
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y_ll = vmlal_n_u16(y_ll, vget_low_u16(g_l), F_0_587);
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y_lh = vmlal_n_u16(y_lh, vget_high_u16(g_l), F_0_587);
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y_hl = vmlal_n_u16(y_hl, vget_low_u16(g_h), F_0_587);
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y_hh = vmlal_n_u16(y_hh, vget_high_u16(g_h), F_0_587);
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y_ll = vmlal_n_u16(y_ll, vget_low_u16(b_l), F_0_113);
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y_lh = vmlal_n_u16(y_lh, vget_high_u16(b_l), F_0_113);
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y_hl = vmlal_n_u16(y_hl, vget_low_u16(b_h), F_0_113);
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y_hh = vmlal_n_u16(y_hh, vget_high_u16(b_h), F_0_113);
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/* Descale Y values (rounding right shift) and narrow to 16-bit. */
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uint16x8_t y_l = vcombine_u16(vrshrn_n_u32(y_ll, 16),
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vrshrn_n_u32(y_lh, 16));
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uint16x8_t y_h = vcombine_u16(vrshrn_n_u32(y_hl, 16),
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vrshrn_n_u32(y_hh, 16));
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/* Narrow Y values to 8-bit and store to memory. Buffer overwrite is
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* permitted up to the next multiple of ALIGN_SIZE bytes.
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*/
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vst1q_u8(outptr, vcombine_u8(vmovn_u16(y_l), vmovn_u16(y_h)));
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/* Increment pointers. */
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inptr += (16 * RGB_PIXELSIZE);
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outptr += 16;
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}
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}
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}
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