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Backends: Enhance pixel manipulation functions for SDL_Surface

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This commit is contained in:
moonpower 2025-12-25 00:03:50 +03:00
parent f2703c1015
commit b3008c0543
1 changed files with 93 additions and 38 deletions
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131
backends/imgui_impl_sdlsurface2.cpp
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@ -10,14 +10,70 @@
static SDL_Surface* g_TargetSurface = nullptr;
static SDL_Surface* g_FontSurface = nullptr;
static inline void PutPixel(SDL_Surface* surface, int x, int y, Uint8 r, Uint8 g, Uint8 b, Uint8 a)
static inline Uint32 GetPixel(SDL_Surface* s, int x, int y)
{
if (x < 0 || y < 0 || x >= surface->w || y >= surface->h) return;
Uint32 pixel = SDL_MapRGBA(surface->format, r, g, b, a);
Uint8* pixels = (Uint8*)surface->pixels;
int pitch = surface->pitch;
Uint32* dst = (Uint32*)(pixels + y * pitch + x * 4);
*dst = pixel;
Uint8* p = (Uint8*)s->pixels + y * s->pitch + x * s->format->BytesPerPixel;
switch (s->format->BytesPerPixel)
{
case 1: return *p;
case 2: return *(Uint16*)p;
case 3:
if (SDL_BYTEORDER == SDL_BIG_ENDIAN)
return (p[0] << 16) | (p[1] << 8) | p[2];
else
return p[0] | (p[1] << 8) | (p[2] << 16);
case 4: return *(Uint32*)p;
}
return 0;
}
static inline void BlendPixel(SDL_Surface* s, int x, int y,
Uint8 sr, Uint8 sg, Uint8 sb, Uint8 sa)
{
if (!s || sa == 0) return;
if (x < 0 || y < 0 || x >= s->w || y >= s->h) return;
Uint32 dst_pix = GetPixel(s, x, y);
Uint8 dr, dg, db, da;
SDL_GetRGBA(dst_pix, s->format, &dr, &dg, &db, &da);
float src_a = sa / 255.0f;
float dst_a = da / 255.0f;
float out_a = src_a + dst_a * (1.0f - src_a);
float out_r = (sr * src_a + dr * dst_a * (1.0f - src_a)) / (out_a > 0 ? out_a : 1.0f);
float out_g = (sg * src_a + dg * dst_a * (1.0f - src_a)) / (out_a > 0 ? out_a : 1.0f);
float out_b = (sb * src_a + db * dst_a * (1.0f - src_a)) / (out_a > 0 ? out_a : 1.0f);
Uint8 fr = (Uint8)std::clamp(out_r, 0.0f, 255.0f);
Uint8 fg = (Uint8)std::clamp(out_g, 0.0f, 255.0f);
Uint8 fb = (Uint8)std::clamp(out_b, 0.0f, 255.0f);
Uint8 fa = (Uint8)std::clamp(out_a * 255.0f, 0.0f, 255.0f);
Uint32 out_pix = SDL_MapRGBA(s->format, fr, fg, fb, fa);
Uint8* p = (Uint8*)s->pixels + y * s->pitch + x * s->format->BytesPerPixel;
switch (s->format->BytesPerPixel)
{
case 1: *p = (Uint8)out_pix; break;
case 2: *(Uint16*)p = (Uint16)out_pix; break;
case 3:
if (SDL_BYTEORDER == SDL_BIG_ENDIAN)
{
p[0] = (out_pix >> 16) & 0xFF;
p[1] = (out_pix >> 8) & 0xFF;
p[2] = out_pix & 0xFF;
}
else
{
p[0] = out_pix & 0xFF;
p[1] = (out_pix >> 8) & 0xFF;
p[2] = (out_pix >> 16) & 0xFF;
}
break;
case 4: *(Uint32*)p = out_pix; break;
}
}
static inline float Edge(const ImVec2& a, const ImVec2& b, float x, float y)
@ -37,8 +93,9 @@ SDL_Surface* ImGui_ImplSDLSurface2_CreateFontAtlasSurface()
if (!surf) return nullptr;
SDL_LockSurface(surf);
memcpy(surf->pixels, pixels, width * height * 4);
std::memcpy(surf->pixels, pixels, width * height * 4);
SDL_UnlockSurface(surf);
SDL_SetSurfaceBlendMode(surf, SDL_BLENDMODE_NONE);
return surf;
}
@ -91,17 +148,20 @@ void ImGui_ImplSDLSurface2_RenderDrawData(ImDrawData* draw_data)
for (int cmd_i = 0; cmd_i < cmd_list->CmdBuffer.Size; cmd_i++)
{
const ImDrawCmd* pcmd = &cmd_list->CmdBuffer[cmd_i];
if (pcmd->ElemCount == 0) { idx_offset += 0; continue; }
if (pcmd->ElemCount == 0)
continue;
ImVec2 clip_min = ImVec2((pcmd->ClipRect.x - display_pos.x) * fb_scale.x,
(pcmd->ClipRect.y - display_pos.y) * fb_scale.y);
ImVec2 clip_max = ImVec2((pcmd->ClipRect.z - display_pos.x) * fb_scale.x,
(pcmd->ClipRect.w - display_pos.y) * fb_scale.y);
ImVec2 clip_min = ImVec2(
(pcmd->ClipRect.x - display_pos.x) * fb_scale.x,
(pcmd->ClipRect.y - display_pos.y) * fb_scale.y);
ImVec2 clip_max = ImVec2(
(pcmd->ClipRect.z - display_pos.x) * fb_scale.x,
(pcmd->ClipRect.w - display_pos.y) * fb_scale.y);
int cx0 = (int)floor(clip_min.x);
int cy0 = (int)floor(clip_min.y);
int cx1 = (int)ceil(clip_max.x);
int cy1 = (int)ceil(clip_max.y);
int cx0 = (int)std::floor(clip_min.x);
int cy0 = (int)std::floor(clip_min.y);
int cx1 = (int)std::ceil (clip_max.x);
int cy1 = (int)std::ceil (clip_max.y);
cx0 = std::max(cx0, 0);
cy0 = std::max(cy0, 0);
@ -114,11 +174,7 @@ void ImGui_ImplSDLSurface2_RenderDrawData(ImDrawData* draw_data)
continue;
}
SDL_Rect srect;
srect.x = cx0;
srect.y = cy0;
srect.w = cx1 - cx0;
srect.h = cy1 - cy0;
SDL_Rect srect{ cx0, cy0, cx1 - cx0, cy1 - cy0 };
SDL_SetClipRect(g_TargetSurface, &srect);
SDL_Surface* tex = (SDL_Surface*)pcmd->GetTexID();
@ -137,10 +193,10 @@ void ImGui_ImplSDLSurface2_RenderDrawData(ImDrawData* draw_data)
ImVec2 p1 = ImVec2((v1.pos.x - display_pos.x) * fb_scale.x, (v1.pos.y - display_pos.y) * fb_scale.y);
ImVec2 p2 = ImVec2((v2.pos.x - display_pos.x) * fb_scale.x, (v2.pos.y - display_pos.y) * fb_scale.y);
int minx = (int)floor(std::min(std::min(p0.x, p1.x), p2.x));
int miny = (int)floor(std::min(std::min(p0.y, p1.y), p2.y));
int maxx = (int)ceil(std::max(std::max(p0.x, p1.x), p2.x));
int maxy = (int)ceil(std::max(std::max(p0.y, p1.y), p2.y));
int minx = (int)std::floor(std::min({ p0.x, p1.x, p2.x }));
int miny = (int)std::floor(std::min({ p0.y, p1.y, p2.y }));
int maxx = (int)std::ceil (std::max({ p0.x, p1.x, p2.x }));
int maxy = (int)std::ceil (std::max({ p0.y, p1.y, p2.y }));
minx = std::max(minx, cx0);
miny = std::max(miny, cy0);
@ -180,37 +236,36 @@ void ImGui_ImplSDLSurface2_RenderDrawData(ImDrawData* draw_data)
float b = w0 * c0[2] + w1 * c1[2] + w2 * c2[2];
float a = w0 * c0[3] + w1 * c1[3] + w2 * c2[3];
Uint8 out_r = (Uint8)(std::min(1.0f, r) * 255.0f);
Uint8 out_g = (Uint8)(std::min(1.0f, g) * 255.0f);
Uint8 out_b = (Uint8)(std::min(1.0f, b) * 255.0f);
Uint8 out_a = (Uint8)(std::min(1.0f, a) * 255.0f);
Uint8 out_r = (Uint8)(std::clamp(r, 0.0f, 1.0f) * 255.0f);
Uint8 out_g = (Uint8)(std::clamp(g, 0.0f, 1.0f) * 255.0f);
Uint8 out_b = (Uint8)(std::clamp(b, 0.0f, 1.0f) * 255.0f);
Uint8 out_a = (Uint8)(std::clamp(a, 0.0f, 1.0f) * 255.0f);
if (tex)
{
ImVec2 uv0 = v0.uv; ImVec2 uv1 = v1.uv; ImVec2 uv2 = v2.uv;
ImVec2 uv0 = v0.uv, uv1 = v1.uv, uv2 = v2.uv;
float u = w0 * uv0.x + w1 * uv1.x + w2 * uv2.x;
float v = w0 * uv0.y + w1 * uv1.y + w2 * uv2.y;
int tx = (int)(u * (tex->w - 1) + 0.5f);
int ty = (int)(v * (tex->h - 1) + 0.5f);
tx = std::clamp(tx, 0, tex->w - 1);
ty = std::clamp(ty, 0, tex->h - 1);
Uint8* tpx = (Uint8*)tex->pixels + ty * tex->pitch + tx * 4;
Uint8 tr = tpx[0];
Uint8 tg = tpx[1];
Uint8 tb = tpx[2];
Uint8 ta = tpx[3];
Uint32 tpx = GetPixel(tex, tx, ty);
Uint8 tr, tg, tb, ta;
SDL_GetRGBA(tpx, tex->format, &tr, &tg, &tb, &ta);
Uint8 final_r = (Uint8)((tr * out_r) / 255);
Uint8 final_g = (Uint8)((tg * out_g) / 255);
Uint8 final_b = (Uint8)((tb * out_b) / 255);
Uint8 final_a = (Uint8)((ta * out_a) / 255);
PutPixel(g_TargetSurface, x, y, final_r, final_g, final_b, final_a);
BlendPixel(g_TargetSurface, x, y, final_r, final_g, final_b, final_a);
}
else
{
PutPixel(g_TargetSurface, x, y, out_r, out_g, out_b, out_a);
BlendPixel(g_TargetSurface, x, y, out_r, out_g, out_b, out_a);
}
}
}