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[Nokia N-Gage] Fix alpha transparency in 4K color mode using BitBltMasked

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Previously, all transparent pixels were rendered as opaque due to the limitations of the 4K color mode. Replaced Gc()->BitBlt() with Gc()->BitBltMasked() and updated the mask during copy operations to correctly respect the alpha channel of textures, while maintaining good performance.
This commit is contained in:
Michael Fitzmayer
2025-06-04 21:05:29 +02:00
parent d86fb8a83a
commit 2ef7944170
2 changed files with 61 additions and 2 deletions
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62
src/render/ngage/SDL_render_ngage.cpp
View File

@@ -69,6 +69,8 @@ void NGAGE_DestroyTextureData(NGAGE_TextureData *data)
if (data) {
delete data->bitmap;
data->bitmap = NULL;
delete data->mask;
data->mask = NULL;
}
}
@@ -350,7 +352,29 @@ bool CRenderer::Copy(SDL_Renderer *renderer, SDL_Texture *texture, const SDL_Rec
if (phdata->bitmap) {
TRect aSource(TPoint(srcrect->x, srcrect->y), TSize(srcrect->w, srcrect->h));
TPoint aDest(dstrect->x, dstrect->y);
iRenderer->Gc()->BitBlt(aDest, phdata->bitmap, aSource);
w = phdata->surface->w;
pitch = phdata->surface->pitch;
Uint16 *src = (Uint16 *)phdata->surface->pixels;
Uint16 *mask = (Uint16 *)phdata->mask->DataAddress();
for (int y = 0; y < srcrect->h; ++y) {
int src_y = srcrect->y + y;
if (src_y < 0 || src_y >= phdata->surface->h) {
continue;
}
for (int x = 0; x < srcrect->w; ++x) {
int src_x = srcrect->x + x;
if (src_x < 0 || src_x >= phdata->surface->w) {
continue;
}
Uint16 pixel = src[src_y * (pitch / 2) + src_x];
Uint8 alpha = (pixel & 0xF000) >> 12;
mask[src_y * w + src_x] = (alpha == 0) ? 0x0000 : 0xFFFF;
}
}
iRenderer->Gc()->BitBltMasked(aDest, phdata->bitmap, aSource, phdata->mask, EFalse);
}
return true;
@@ -416,7 +440,29 @@ bool CRenderer::CopyEx(SDL_Renderer *renderer, SDL_Texture *texture, const NGAGE
if (phdata->bitmap) {
TRect aSource(TPoint(copydata->srcrect.x, copydata->srcrect.y), TSize(copydata->srcrect.w, copydata->srcrect.h));
TPoint aDest(copydata->dstrect.x, copydata->dstrect.y);
iRenderer->Gc()->BitBlt(aDest, phdata->bitmap, aSource);
w = phdata->surface->w;
pitch = phdata->surface->pitch;
Uint16 *src = (Uint16 *)phdata->surface->pixels;
Uint16 *mask = (Uint16 *)phdata->mask->DataAddress();
for (int y = 0; y < copydata->srcrect.h; ++y) {
int src_y = copydata->srcrect.y + y;
if (src_y < 0 || src_y >= phdata->surface->h) {
continue;
}
for (int x = 0; x < copydata->srcrect.w; ++x) {
int src_x = copydata->srcrect.x + x;
if (src_x < 0 || src_x >= phdata->surface->w) {
continue;
}
Uint16 pixel = src[src_y * (pitch / 2) + src_x];
Uint8 alpha = (pixel & 0xF000) >> 12;
mask[src_y * w + src_x] = (alpha == 0) ? 0x0000 : 0xFFFF;
}
}
iRenderer->Gc()->BitBltMasked(aDest, phdata->bitmap, aSource, phdata->mask, EFalse);
}
return true;
@@ -440,6 +486,18 @@ bool CRenderer::CreateTextureData(NGAGE_TextureData *aTextureData, const TInt aW
return false;
}
aTextureData->mask = new CFbsBitmap();
if (!aTextureData->mask) {
return false;
}
error = aTextureData->mask->Create(TSize(aWidth, aHeight), EColor4K);
if (error != KErrNone) {
delete aTextureData->mask;
aTextureData->mask = NULL;
return false;
}
return true;
}

1
src/render/ngage/SDL_render_ngage_c.h
View File

@@ -58,6 +58,7 @@ typedef struct CFbsBitmap CFbsBitmap;
typedef struct NGAGE_TextureData
{
CFbsBitmap *bitmap;
CFbsBitmap *mask;
SDL_Surface *surface;
} NGAGE_TextureData;