New example: textures_magnifying_glass (#5587)

Author: BadRAM

examples/textures/textures_magnifying_glass.c

@@ -0,0 +1,134 @@
+/*******************************************************************************************
+*
+*   raylib textures example - magnifying glass
+*
+*   Example complexity rating: [★★★☆] 3/4
+* 
+*   Example originally created with raylib 5.6, last time updated with raylib 5.6
+*
+*   Example contributed by Luke Vaughan (@badram) and reviewed by Ramon Santamaria (@raysan5)
+*
+*   Example licensed under an unmodified zlib/libpng license, which is an OSI-certified,
+*   BSD-like license that allows static linking with closed source software
+*
+*   Copyright (c) 2026 Luke Vaughan (@badram)
+*
+********************************************************************************************/
+
+#include "raylib.h"
+#include "rlgl.h" // for rlSetBlendFactorsSeparate()
+
+//------------------------------------------------------------------------------------
+// Program main entry point
+//------------------------------------------------------------------------------------
+int main(void)
+{
+    // Initialization
+    //--------------------------------------------------------------------------------------
+    const int screenWidth = 800;
+    const int screenHeight = 450;
+
+    InitWindow(screenWidth, screenHeight, "raylib [textures] example - magnifying glass");
+        
+    Texture2D bunny = LoadTexture("resources/raybunny.png");
+    Texture2D parrots = LoadTexture("resources/parrots.png");
+    
+    // Use image draw to generate a mask texture instead of loading it from a file.
+    Image circle = GenImageColor(256, 256, BLANK);
+    ImageDrawCircle(&circle, 128, 128, 128, WHITE);
+    Texture2D mask = LoadTextureFromImage(circle); // Copy the mask image from RAM to VRAM
+    UnloadImage(circle); // Unload the image from RAM
+    
+    RenderTexture2D magnifiedWorld = LoadRenderTexture(256, 256);
+    
+    Camera2D camera = { 0 };
+    // Set magnifying glass zoom
+    camera.zoom = 2;
+    // Offset by half the size of the magnifying glass to counteract drawing the texture centered on the mouse position
+    camera.offset = (Vector2){128, 128};
+
+
+    SetTargetFPS(60);
+    //--------------------------------------------------------------------------------------
+
+    // Main game loop
+    while (!WindowShouldClose())    // Detect window close button or ESC key
+    {
+        // Update
+        //----------------------------------------------------------------------------------
+        Vector2 mPos = GetMousePosition();
+        camera.target = mPos;
+
+        //----------------------------------------------------------------------------------
+
+        // Draw
+        //----------------------------------------------------------------------------------
+        BeginDrawing();
+
+            ClearBackground(RAYWHITE);
+
+            // Draw the normal version of the world
+            DrawTexture(parrots, 144, 33, WHITE);
+            DrawText("Use the magnifying glass to find hidden bunnies!", 154, 6, 20, BLACK);
+
+            // Render to a the magnifying glass 
+            BeginTextureMode(magnifiedWorld);
+                ClearBackground(RAYWHITE);
+
+                BeginMode2D(camera);
+                    // Draw the same things in the magnified world as were in the normal version
+                    DrawTexture(parrots, 144, 33, WHITE);
+                    DrawText("Use the magnifying glass to find hidden bunnies!", 154, 6, 20, BLACK);
+
+                    // Draw bunnies only in the magnified world.
+                    // BLEND_MULTIPLIED lets them take on the color of the image below them.
+                    BeginBlendMode(BLEND_MULTIPLIED);
+                        DrawTexture(bunny, 250, 350, WHITE);
+                        DrawTexture(bunny, 500, 100, WHITE);
+                        DrawTexture(bunny, 420, 300, WHITE);
+                        DrawTexture(bunny, 650, 10, WHITE);
+                    EndBlendMode();
+                EndMode2D();
+
+                // Mask the magnifying glass view texture to a circle
+                // To make the mask affect only alpha, a CUSTOM blend mode is used with SEPARATE color/alpha functions
+                BeginBlendMode(BLEND_CUSTOM_SEPARATE);
+                    // C: Color, A: Alpha, s: source (texture to draw), d: destination (texture drawn to)
+                    //   glSrcRGB: RL_ZERO      - Cs * 0 = 0  - discard source rgb because we don't want to draw our texture's colors at all
+                    //   glDstRGB: RL_ONE       - Cd * 1 = Cd - use destination colors unmodified
+                    //   glSrcAlpha: RL_ONE     - As * 1 = As - use source alpha unmodified
+                    //   glDstAlpha: RL_ZERO    - Ad * 0 = 0  - discard destination alpha
+                    //   glEqRGB: RL_FUNC_ADD   - Cs(0) + Cd = Cd - destination color is unmodified
+                    //   glEqAlpha: RL_FUNC_ADD - As + Ad(0) = As - destination alpha is set to source alpha
+                    rlSetBlendFactorsSeparate(RL_ZERO, RL_ONE, RL_ONE, RL_ZERO, RL_FUNC_ADD, RL_FUNC_ADD);
+                    DrawTexture(mask, 0, 0, WHITE);
+                EndBlendMode();
+            EndTextureMode();
+
+            // Draw magnifiedWorld to screen, centered on cursor
+            DrawTextureRec(magnifiedWorld.texture, (Rectangle){0, 0, 256, -256}, (Vector2){mPos.x - 128, mPos.y - 128}, WHITE);
+
+            // Draw the outer ring of the magnifying glass
+            DrawRing(mPos, 126, 130, 0, 360, 64, BLACK);
+
+            // Draw floating specular highlight on the glass
+            float rx = mPos.x/800;
+            float ry = mPos.y/800;
+            DrawCircle((int)(mPos.x - 64*rx) - 32, (int)(mPos.y - 64*ry) - 32, 4, ColorAlpha(WHITE, 0.5));
+
+        EndDrawing();
+        //----------------------------------------------------------------------------------
+    }
+
+    // De-Initialization
+    //--------------------------------------------------------------------------------------
+    UnloadTexture(parrots);
+    UnloadTexture(bunny);
+    UnloadTexture(mask);
+    UnloadRenderTexture(magnifiedWorld);
+
+    CloseWindow();        // Close window and OpenGL context
+    //--------------------------------------------------------------------------------------
+
+    return 0;
+}