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Set the alpha opaque when blending to an RGB format

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Fixes the render_testRGBSurfaceNoAlpha automated test in sdl2-compat

(cherry picked from commit 7bb95bde49)
This commit is contained in:
Sam Lantinga
2025-03-30 21:24:53 -07:00
parent 6b665066f0
commit 4d966ff546
5 changed files with 83 additions and 42 deletions
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52
src/video/SDL_blit_A.c
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@@ -22,6 +22,7 @@
#ifdef SDL_HAVE_BLIT_A
#include "SDL_pixels_c.h"
#include "SDL_surface_c.h"
// Functions to perform alpha blended blitting
@@ -968,6 +969,10 @@ static void Blit8888to8888PixelAlphaSwizzle(SDL_BlitInfo *info)
int dstskip = info->dst_skip;
const SDL_PixelFormatDetails *srcfmt = info->src_fmt;
const SDL_PixelFormatDetails *dstfmt = info->dst_fmt;
bool fill_alpha = !dstfmt->Amask;
Uint32 dstAmask, dstAshift;
SDL_Get8888AlphaMaskAndShift(dstfmt, &dstAmask, &dstAshift);
while (height--) {
int i = 0;
@@ -976,6 +981,9 @@ static void Blit8888to8888PixelAlphaSwizzle(SDL_BlitInfo *info)
Uint32 src32 = *(Uint32 *)src;
Uint32 dst32 = *(Uint32 *)dst;
ALPHA_BLEND_SWIZZLE_8888(src32, dst32, srcfmt, dstfmt);
if (fill_alpha) {
dst32 |= dstAmask;
}
*(Uint32 *)dst = dst32;
src += 4;
dst += 4;
@@ -998,6 +1006,10 @@ static void SDL_TARGETING("sse4.1") Blit8888to8888PixelAlphaSwizzleSSE41(SDL_Bli
int dstskip = info->dst_skip;
const SDL_PixelFormatDetails *srcfmt = info->src_fmt;
const SDL_PixelFormatDetails *dstfmt = info->dst_fmt;
bool fill_alpha = !dstfmt->Amask;
Uint32 dstAmask, dstAshift;
SDL_Get8888AlphaMaskAndShift(dstfmt, &dstAmask, &dstAshift);
// The byte offsets for the start of each pixel
const __m128i mask_offsets = _mm_set_epi8(
@@ -1011,7 +1023,7 @@ static void SDL_TARGETING("sse4.1") Blit8888to8888PixelAlphaSwizzleSSE41(SDL_Bli
mask_offsets);
const __m128i alpha_splat_mask = _mm_add_epi8(_mm_set1_epi8(srcfmt->Ashift >> 3), mask_offsets);
const __m128i alpha_fill_mask = _mm_set1_epi32((int)dstfmt->Amask);
const __m128i alpha_fill_mask = _mm_set1_epi32((int)dstAmask);
while (height--) {
int i = 0;
@@ -1057,7 +1069,11 @@ static void SDL_TARGETING("sse4.1") Blit8888to8888PixelAlphaSwizzleSSE41(SDL_Bli
dst_hi = _mm_mulhi_epu16(dst_hi, _mm_set1_epi16(257));
// Blend the pixels together and save the result
_mm_storeu_si128((__m128i *)dst, _mm_packus_epi16(dst_lo, dst_hi));
dst128 = _mm_packus_epi16(dst_lo, dst_hi);
if (fill_alpha) {
dst128 = _mm_or_si128(dst128, alpha_fill_mask);
}
_mm_storeu_si128((__m128i *)dst, dst128);
src += 16;
dst += 16;
@@ -1067,6 +1083,9 @@ static void SDL_TARGETING("sse4.1") Blit8888to8888PixelAlphaSwizzleSSE41(SDL_Bli
Uint32 src32 = *(Uint32 *)src;
Uint32 dst32 = *(Uint32 *)dst;
ALPHA_BLEND_SWIZZLE_8888(src32, dst32, srcfmt, dstfmt);
if (fill_alpha) {
dst32 |= dstAmask;
}
*(Uint32 *)dst = dst32;
src += 4;
dst += 4;
@@ -1091,6 +1110,10 @@ static void SDL_TARGETING("avx2") Blit8888to8888PixelAlphaSwizzleAVX2(SDL_BlitIn
int dstskip = info->dst_skip;
const SDL_PixelFormatDetails *srcfmt = info->src_fmt;
const SDL_PixelFormatDetails *dstfmt = info->dst_fmt;
bool fill_alpha = !dstfmt->Amask;
Uint32 dstAmask, dstAshift;
SDL_Get8888AlphaMaskAndShift(dstfmt, &dstAmask, &dstAshift);
// The byte offsets for the start of each pixel
const __m256i mask_offsets = _mm256_set_epi8(
@@ -1104,7 +1127,7 @@ static void SDL_TARGETING("avx2") Blit8888to8888PixelAlphaSwizzleAVX2(SDL_BlitIn
mask_offsets);
const __m256i alpha_splat_mask = _mm256_add_epi8(_mm256_set1_epi8(srcfmt->Ashift >> 3), mask_offsets);
const __m256i alpha_fill_mask = _mm256_set1_epi32((int)dstfmt->Amask);
const __m256i alpha_fill_mask = _mm256_set1_epi32((int)dstAmask);
while (height--) {
int i = 0;
@@ -1150,7 +1173,11 @@ static void SDL_TARGETING("avx2") Blit8888to8888PixelAlphaSwizzleAVX2(SDL_BlitIn
dst_hi = _mm256_mulhi_epu16(dst_hi, _mm256_set1_epi16(257));
// Blend the pixels together and save the result
_mm256_storeu_si256((__m256i *)dst, _mm256_packus_epi16(dst_lo, dst_hi));
dst256 = _mm256_packus_epi16(dst_lo, dst_hi);
if (fill_alpha) {
dst256 = _mm256_or_si256(dst256, alpha_fill_mask);
}
_mm256_storeu_si256((__m256i *)dst, dst256);
src += 32;
dst += 32;
@@ -1160,6 +1187,9 @@ static void SDL_TARGETING("avx2") Blit8888to8888PixelAlphaSwizzleAVX2(SDL_BlitIn
Uint32 src32 = *(Uint32 *)src;
Uint32 dst32 = *(Uint32 *)dst;
ALPHA_BLEND_SWIZZLE_8888(src32, dst32, srcfmt, dstfmt);
if (fill_alpha) {
dst32 |= dstAmask;
}
*(Uint32 *)dst = dst32;
src += 4;
dst += 4;
@@ -1184,6 +1214,10 @@ static void Blit8888to8888PixelAlphaSwizzleNEON(SDL_BlitInfo *info)
int dstskip = info->dst_skip;
const SDL_PixelFormatDetails *srcfmt = info->src_fmt;
const SDL_PixelFormatDetails *dstfmt = info->dst_fmt;
bool fill_alpha = !dstfmt->Amask;
Uint32 dstAmask, dstAshift;
SDL_Get8888AlphaMaskAndShift(dstfmt, &dstAmask, &dstAshift);
// The byte offsets for the start of each pixel
const uint8x16_t mask_offsets = vreinterpretq_u8_u64(vcombine_u64(
@@ -1197,7 +1231,7 @@ static void Blit8888to8888PixelAlphaSwizzleNEON(SDL_BlitInfo *info)
((srcfmt->Bshift >> 3) << dstfmt->Bshift))));
const uint8x16_t alpha_splat_mask = vaddq_u8(vdupq_n_u8(srcfmt->Ashift >> 3), mask_offsets);
const uint8x16_t alpha_fill_mask = vreinterpretq_u8_u32(vdupq_n_u32(dstfmt->Amask));
const uint8x16_t alpha_fill_mask = vreinterpretq_u8_u32(vdupq_n_u32(dstAmask));
while (height--) {
int i = 0;
@@ -1242,6 +1276,10 @@ static void Blit8888to8888PixelAlphaSwizzleNEON(SDL_BlitInfo *info)
// temp = vraddhn_u16(res_lo, vrshrq_n_u16(res_lo, 8));
// dst128 = vraddhn_high_u16(temp, res_hi, vrshrq_n_u16(res_hi, 8));
if (fill_alpha) {
dst128 = vorrq_u8(dst128, alpha_fill_mask);
}
// Save the result
vst1q_u8(dst, dst128);
@@ -1266,6 +1304,10 @@ static void Blit8888to8888PixelAlphaSwizzleNEON(SDL_BlitInfo *info)
dst32 = vaddhn_u16(res, vshrq_n_u16(res, 8));
if (fill_alpha) {
dst32 = vorr_u8(dst32, vget_low_u8(alpha_fill_mask));
}
// Save the result, only low 32-bits
vst1_lane_u32((Uint32*)dst, vreinterpret_u32_u8(dst32), 0);

42
src/video/SDL_blit_N.c
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@@ -2568,36 +2568,6 @@ static void BlitNtoNKeyCopyAlpha(SDL_BlitInfo *info)
dstAmask; \
} while (0)
#if defined(SDL_SSE4_1_INTRINSICS) || defined(SDL_AVX2_INTRINSICS) || (defined(SDL_NEON_INTRINSICS) && (__ARM_ARCH >= 8))
static void Get8888AlphaMaskAndShift(const SDL_PixelFormatDetails *fmt, Uint32 *mask, Uint32 *shift)
{
if (fmt->Amask) {
*mask = fmt->Amask;
*shift = fmt->Ashift;
} else {
*mask = ~(fmt->Rmask | fmt->Gmask | fmt->Bmask);
switch (*mask) {
case 0x000000FF:
*shift = 0;
break;
case 0x0000FF00:
*shift = 8;
break;
case 0x00FF0000:
*shift = 16;
break;
case 0xFF000000:
*shift = 24;
break;
default:
// Should never happen
*shift = 0;
break;
}
}
}
#endif // SSE4.1, AVX2, and NEON implementations of Blit8888to8888PixelSwizzle
#ifdef SDL_SSE4_1_INTRINSICS
static void SDL_TARGETING("sse4.1") Blit8888to8888PixelSwizzleSSE41(SDL_BlitInfo *info)
@@ -2614,8 +2584,8 @@ static void SDL_TARGETING("sse4.1") Blit8888to8888PixelSwizzleSSE41(SDL_BlitInfo
Uint32 srcAmask, srcAshift;
Uint32 dstAmask, dstAshift;
Get8888AlphaMaskAndShift(srcfmt, &srcAmask, &srcAshift);
Get8888AlphaMaskAndShift(dstfmt, &dstAmask, &dstAshift);
SDL_Get8888AlphaMaskAndShift(srcfmt, &srcAmask, &srcAshift);
SDL_Get8888AlphaMaskAndShift(dstfmt, &dstAmask, &dstAshift);
// The byte offsets for the start of each pixel
const __m128i mask_offsets = _mm_set_epi8(
@@ -2689,8 +2659,8 @@ static void SDL_TARGETING("avx2") Blit8888to8888PixelSwizzleAVX2(SDL_BlitInfo *i
Uint32 srcAmask, srcAshift;
Uint32 dstAmask, dstAshift;
Get8888AlphaMaskAndShift(srcfmt, &srcAmask, &srcAshift);
Get8888AlphaMaskAndShift(dstfmt, &dstAmask, &dstAshift);
SDL_Get8888AlphaMaskAndShift(srcfmt, &srcAmask, &srcAshift);
SDL_Get8888AlphaMaskAndShift(dstfmt, &dstAmask, &dstAshift);
// The byte offsets for the start of each pixel
const __m256i mask_offsets = _mm256_set_epi8(
@@ -2764,8 +2734,8 @@ static void Blit8888to8888PixelSwizzleNEON(SDL_BlitInfo *info)
Uint32 srcAmask, srcAshift;
Uint32 dstAmask, dstAshift;
Get8888AlphaMaskAndShift(srcfmt, &srcAmask, &srcAshift);
Get8888AlphaMaskAndShift(dstfmt, &dstAmask, &dstAshift);
SDL_Get8888AlphaMaskAndShift(srcfmt, &srcAmask, &srcAshift);
SDL_Get8888AlphaMaskAndShift(dstfmt, &dstAmask, &dstAshift);
// The byte offsets for the start of each pixel
const uint8x16_t mask_offsets = vreinterpretq_u8_u64(vcombine_u64(

28
src/video/SDL_pixels.c
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@@ -692,6 +692,34 @@ void SDL_QuitPixelFormatDetails(void)
}
}
void SDL_Get8888AlphaMaskAndShift(const SDL_PixelFormatDetails *fmt, Uint32 *mask, Uint32 *shift)
{
if (fmt->Amask) {
*mask = fmt->Amask;
*shift = fmt->Ashift;
} else {
*mask = ~(fmt->Rmask | fmt->Gmask | fmt->Bmask);
switch (*mask) {
case 0x000000FF:
*shift = 0;
break;
case 0x0000FF00:
*shift = 8;
break;
case 0x00FF0000:
*shift = 16;
break;
case 0xFF000000:
*shift = 24;
break;
default:
// Should never happen
*shift = 0;
break;
}
}
}
SDL_Colorspace SDL_GetDefaultColorspaceForFormat(SDL_PixelFormat format)
{
if (SDL_ISPIXELFORMAT_FOURCC(format)) {

2
src/video/SDL_pixels_c.h
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@@ -29,7 +29,7 @@
// Pixel format functions
extern bool SDL_CalculateSurfaceSize(SDL_PixelFormat format, int width, int height, size_t *size, size_t *pitch, bool minimalPitch);
extern void SDL_Get8888AlphaMaskAndShift(const SDL_PixelFormatDetails *fmt, Uint32 *mask, Uint32 *shift);
extern SDL_Colorspace SDL_GetDefaultColorspaceForFormat(SDL_PixelFormat pixel_format);
extern void SDL_QuitPixelFormatDetails(void);

1
src/video/SDL_surface_c.h
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@@ -83,6 +83,7 @@ struct SDL_Surface
// Surface functions
extern bool SDL_SurfaceValid(SDL_Surface *surface);
extern void SDL_UpdateSurfaceLockFlag(SDL_Surface *surface);
extern bool SDL_CalculateSurfaceSize(SDL_PixelFormat format, int width, int height, size_t *size, size_t *pitch, bool minimalPitch);
extern float SDL_GetDefaultSDRWhitePoint(SDL_Colorspace colorspace);
extern float SDL_GetSurfaceSDRWhitePoint(SDL_Surface *surface, SDL_Colorspace colorspace);
extern float SDL_GetDefaultHDRHeadroom(SDL_Colorspace colorspace);