<?phpnamespace App\Gfx;/** * Options > FILTRE CRT: an old TV look drawn over the scaled picture, in one or two copies per frame: * - scanlines: the lower part of every line of the game picture is darkened; * - vignette: the corners get darker, smoothly. * Both are RGBA surfaces turned into textures (a surface with an alpha channel gives a blended texture: * the SDL extension has no SDL_SetTextureBlendMode / SDL_SetRenderDrawBlendMode), made again only when * the size of the picture changes. */class CrtFilter{ private const SCANLINE_ALPHA = 105; // darkness of a scanline (0-255) private const VIGNETTE_ALPHA = 150; // darkness of the corners private const VIGNETTE_SIZE = 48; // the vignette is computed small, then smoothly stretched private mixed $scanlines = null; private mixed $vignette = null; private string $key = ''; public function __construct(private View $renderer) { } /** Draws the filter over $dst, the picture of $viewHeight game lines scaled on the window. */ public function draw(\SDL_Rect $dst, int $viewHeight): void { if ($dst->w <= 0 || $dst->h <= 0 || $viewHeight <= 0) return; $key = $dst->h . 'x' . $viewHeight; if ($key !== $this->key) { $this->free(); $this->scanlines = $this->makeScanlines($dst->h, $viewHeight); $this->vignette ??= $this->makeVignette(); $this->key = $key; } $sdlRenderer = $this->renderer->getRenderer(); if ($this->scanlines) \SDL_RenderCopy($sdlRenderer, $this->scanlines, null, $dst); if ($this->vignette) \SDL_RenderCopy($sdlRenderer, $this->vignette, null, $dst); } public function free(): void { if ($this->scanlines) \SDL_DestroyTexture($this->scanlines); $this->scanlines = null; $this->key = ''; } /** 1 pixel wide, as high as the picture on screen: stretched across it. */ private function makeScanlines(int $height, int $lines): mixed { $surface = $this->surface(1, $height); if (!$surface) return null; $scale = $height / $lines; $rect = new \SDL_Rect; for ($i = 0; $i < $lines; $i++) { $top = (int)floor($i * $scale); $bottom = (int)floor(($i + 1) * $scale); $rows = $bottom - $top; if ($rows <= 0) continue; if ($rows === 1) { // a game line on one screen line (small window): every other line, lighter if ($i % 2) $this->fill($surface, $rect, 0, $top, 1, 1, (int)(self::SCANLINE_ALPHA * 0.6)); continue; } // the lower ~40% of the line is dark, the first screen line of the dark part a bit less $dark = max(1, (int)round($rows * 0.4)); $this->fill($surface, $rect, 0, $bottom - $dark, 1, $dark, self::SCANLINE_ALPHA); if ($dark >= 3) $this->fill($surface, $rect, 0, $bottom - $dark, 1, 1, (int)(self::SCANLINE_ALPHA * 0.6)); } return $this->texture($surface, false); } /** Darker towards the corners (squared distance from the centre, on an ellipse). */ private function makeVignette(): mixed { $n = self::VIGNETTE_SIZE; $surface = $this->surface($n, $n); if (!$surface) return null; $rect = new \SDL_Rect; for ($y = 0; $y < $n; $y++) { for ($x = 0; $x < $n; $x++) { $dx = ($x + 0.5) / $n * 2 - 1; $dy = ($y + 0.5) / $n * 2 - 1; $d = sqrt($dx * $dx * 0.7 + $dy * $dy * 0.7); $alpha = (int)round(self::VIGNETTE_ALPHA * max(0, min(1, ($d - 0.55) / 0.6)) ** 2); if ($alpha > 0) $this->fill($surface, $rect, $x, $y, 1, 1, $alpha); } } return $this->texture($surface, true); } /** Transparent RGBA surface. The alpha mask is written -0x1000000 (0xFF000000): it must fit a 32-bit PHP int (wasm). */ private function surface(int $w, int $h): mixed { return \SDL_CreateRGBSurface(0, $w, $h, 32, 0x000000FF, 0x0000FF00, 0x00FF0000, -0x1000000) ?: null; } private function fill($surface, \SDL_Rect $rect, int $x, int $y, int $w, int $h, int $alpha): void { [$rect->x, $rect->y, $rect->w, $rect->h] = [$x, $y, $w, $h]; \SDL_FillRect($surface, $rect, \SDL_MapRGBA($surface->format, 0, 0, 0, $alpha)); } private function texture($surface, bool $smooth): mixed { // the scale quality is read when the texture is created; the game keeps "0" (crisp pixels) \SDL_SetHint(\SDL_HINT_RENDER_SCALE_QUALITY, $smooth ? "1" : "0"); $texture = \SDL_CreateTextureFromSurface($this->renderer->getRenderer(), $surface); \SDL_SetHint(\SDL_HINT_RENDER_SCALE_QUALITY, "0"); \SDL_FreeSurface($surface); return $texture ?: null; }}