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/* palette_neon_intrinsics.c - NEON optimised palette expansion functions
*
* Copyright (c) 2018-2026 Cosmin Truta
* Copyright (c) 2017-2018 Arm Holdings. All rights reserved.
* Written by Richard Townsend <Richard.Townsend@arm.com>, February 2017.
*
* This code is released under the libpng license.
* For conditions of distribution and use, see the disclaimer
* and license in png.h
*/
#include "../pngpriv.h"
#if PNG_ARM_NEON_IMPLEMENTATION == 1
#if defined(_MSC_VER) && !defined(__clang__) && defined(_M_ARM64)
# include <arm64_neon.h>
#else
# include <arm_neon.h>
#endif
/* Build an RGBA8 palette from the separate RGB and alpha palettes. */
void
png_riffle_palette_neon(png_structrp png_ptr)
{
png_const_colorp palette = png_ptr->palette;
png_bytep riffled_palette = png_ptr->riffled_palette;
png_const_bytep trans_alpha = png_ptr->trans_alpha;
int num_trans = png_ptr->num_trans;
int i;
/* Initially black, opaque. */
uint8x16x4_t w = {{
vdupq_n_u8(0x00),
vdupq_n_u8(0x00),
vdupq_n_u8(0x00),
vdupq_n_u8(0xff),
}};
png_debug(1, "in png_riffle_palette_neon");
/* First, riffle the RGB colours into an RGBA8 palette.
* The alpha component is set to opaque for now.
*/
for (i = 0; i < 256; i += 16)
{
uint8x16x3_t v = vld3q_u8((png_const_bytep)(palette + i));
w.val[0] = v.val[0];
w.val[1] = v.val[1];
w.val[2] = v.val[2];
vst4q_u8(riffled_palette + i * 4, w);
}
/* Fix up the missing transparency values. */
for (i = 0; i < num_trans; i++)
riffled_palette[i * 4 + 3] = trans_alpha[i];
}
/* Expands a palettized row into RGBA8. */
int
png_do_expand_palette_rgba8_neon(png_structrp png_ptr, png_row_infop row_info,
png_const_bytep row, png_bytepp ssp, png_bytepp ddp)
{
png_uint_32 row_width = row_info->width;
const png_uint_32 *riffled_palette =
png_aligncastconst(png_const_uint_32p, png_ptr->riffled_palette);
const png_uint_32 pixels_per_chunk = 4;
png_uint_32 i;
png_debug(1, "in png_do_expand_palette_rgba8_neon");
PNG_UNUSED(row)
if (row_width < pixels_per_chunk)
return 0;
/* This function originally gets the last byte of the output row.
* The NEON part writes forward from a given position, so we have
* to seek this back by 4 pixels x 4 bytes.
*/
*ddp = *ddp - (pixels_per_chunk * 4 - 1);
for (i = 0; i + pixels_per_chunk <= row_width; i += pixels_per_chunk)
{
uint32x4_t cur;
png_bytep sp = *ssp - i, dp = *ddp - i * 4;
cur = vld1q_dup_u32 (riffled_palette + *(sp - 3));
cur = vld1q_lane_u32(riffled_palette + *(sp - 2), cur, 1);
cur = vld1q_lane_u32(riffled_palette + *(sp - 1), cur, 2);
cur = vld1q_lane_u32(riffled_palette + *(sp - 0), cur, 3);
vst1q_u32((void *)dp, cur);
}
/* Undo the pre-adjustment of *ddp before the pointer handoff,
* so the scalar fallback in pngrtran.c receives a dp that points
* to the correct position.
*/
*ddp = *ddp + (pixels_per_chunk * 4 - 1);
*ssp = *ssp - i;
*ddp = *ddp - i * 4;
return i;
}
/* Expands a palettized row into RGB8. */
int
png_do_expand_palette_rgb8_neon(png_structrp png_ptr, png_row_infop row_info,
png_const_bytep row, png_bytepp ssp, png_bytepp ddp)
{
png_uint_32 row_width = row_info->width;
png_const_bytep palette = (png_const_bytep)png_ptr->palette;
const png_uint_32 pixels_per_chunk = 8;
png_uint_32 i;
png_debug(1, "in png_do_expand_palette_rgb8_neon");
PNG_UNUSED(row)
if (row_width <= pixels_per_chunk)
return 0;
/* Seeking this back by 8 pixels x 3 bytes. */
*ddp = *ddp - (pixels_per_chunk * 3 - 1);
for (i = 0; i + pixels_per_chunk <= row_width; i += pixels_per_chunk)
{
uint8x8x3_t cur;
png_bytep sp = *ssp - i, dp = *ddp - i * 3;
cur = vld3_dup_u8(palette + *(sp - 7) * 3);
cur = vld3_lane_u8(palette + *(sp - 6) * 3, cur, 1);
cur = vld3_lane_u8(palette + *(sp - 5) * 3, cur, 2);
cur = vld3_lane_u8(palette + *(sp - 4) * 3, cur, 3);
cur = vld3_lane_u8(palette + *(sp - 3) * 3, cur, 4);
cur = vld3_lane_u8(palette + *(sp - 2) * 3, cur, 5);
cur = vld3_lane_u8(palette + *(sp - 1) * 3, cur, 6);
cur = vld3_lane_u8(palette + *(sp - 0) * 3, cur, 7);
vst3_u8((void *)dp, cur);
}
/* Undo the pre-adjustment of *ddp before the pointer handoff,
* so the scalar fallback in pngrtran.c receives a dp that points
* to the correct position.
*/
*ddp = *ddp + (pixels_per_chunk * 3 - 1);
*ssp = *ssp - i;
*ddp = *ddp - i * 3;
return i;
}
#endif /* PNG_ARM_NEON_IMPLEMENTATION */