Added pixel-perfect camera example

Added pixel-perfect camera example, both the .c file and the cover .png image. The example works with any resolution you want, as long as the ratio stays the same
(ex. 16:9, 4:3) ecc.

examples/core/core_2d_camera_smooth_pixelperfect.c

@@ -0,0 +1,133 @@
+/*******************************************************************************************
+*
+*   raylib [core] example - smooth pixel-perfect camera
+*
+*   This example has been created using raylib 3.7 (www.raylib.com)
+*   raylib is licensed under an unmodified zlib/libpng license (View raylib.h for details)
+*
+*   Example contributed by Giancamillo Alessandroni ([discord]NotManyIdeas#9972 - [github]NotManyIdeasDev) and
+*   reviewed by Ramon Santamaria (@raysan5)
+*
+*   Copyright (c) 2021 Giancamillo Alessandroni (NotManyIdeas#9972) and Ramon Santamaria (@raysan5)
+*
+********************************************************************************************/
+
+#include "raylib.h"
+#include <math.h>
+
+int main(void)
+{
+    // Initialization
+    //--------------------------------------------------------------------------------------
+    const int screenWidth = 800;
+    const int screenHeight = 450;
+
+    const int virualScreenWidth = 160;
+    const int virtualScreenHeight = 90;
+
+    const float virtualRatio = (float)screenWidth / (float)virualScreenWidth;
+
+    InitWindow(screenWidth, screenHeight, "raylib [core] example - smooth pixel-perfect camera");
+
+    Camera2D worldSpaceCamera = { 0 }; // Game world camera
+    worldSpaceCamera.zoom = 1.0f;
+
+    Camera2D screenSpaceCamera = { 0 }; //Smoothing camera
+    screenSpaceCamera.zoom = 1.0f;
+
+    RenderTexture2D renderTexture = LoadRenderTexture(virualScreenWidth, virtualScreenHeight); //This is where we'll draw all our objects.
+
+    Rectangle firstRectangle = { 70.0f, 35.0f, 20.0f, 20.0f };
+    Rectangle secondRectangle = { 90.0f, 55.0f, 30.0f, 10.0f };
+    Rectangle thirdRectangle = { 80.0f, 65.0f, 15.0f, 25.0f };
+
+    Vector2 origin = { 0.0f, 0.0f };
+    float rotation = 0.0f;
+
+    float cameraX = 0.0f;
+    float cameraY = 0.0f;
+
+    SetTargetFPS(60);
+    //--------------------------------------------------------------------------------------
+
+    // Main game loop
+    while (!WindowShouldClose())    // Detect window close button or ESC key
+    {
+        // Update
+        //----------------------------------------------------------------------------------
+        rotation++; // Rotate the rectangles.
+
+        // Make the camera move to demonstrate the effect.
+        cameraX = (sin(GetTime()) * 50.0f) - 10.0f;
+        cameraY = cos(GetTime()) * 30.0f;
+
+        screenSpaceCamera.target = { cameraX, cameraY };
+
+        if (screenSpaceCamera.target.x >= 1 || screenSpaceCamera.target.x <= -1) // Round worldCamera's X, keep the decimals on screenSpaceCamera.
+        {
+            worldSpaceCamera.target.x = (int)screenSpaceCamera.target.x;
+            screenSpaceCamera.target.x -= worldSpaceCamera.target.x;
+            screenSpaceCamera.target.x *= virtualRatio;
+        }
+
+        if (screenSpaceCamera.target.y >= 1 || screenSpaceCamera.target.y <= -1) // Round worldCamera's Y, keep the decimals on screenSpaceCamera.
+        {
+            worldSpaceCamera.target.y = (int)screenSpaceCamera.target.y;
+            screenSpaceCamera.target.y -= worldSpaceCamera.target.y;
+            screenSpaceCamera.target.y *= virtualRatio;
+        }
+
+        //----------------------------------------------------------------------------------
+
+        // Draw
+        //----------------------------------------------------------------------------------
+        BeginDrawing();
+        ClearBackground(RED); // This is for debug purposes. If you see red, then you've probably done something wrong.
+
+        BeginTextureMode(renderTexture);
+
+        BeginMode2D(worldSpaceCamera);
+
+        ClearBackground(RAYWHITE); // This is the color you should see as background color.
+
+        // Draw the rectangles
+        DrawRectanglePro(firstRectangle, origin, rotation, BLACK);
+        DrawRectanglePro(secondRectangle, origin, -rotation, RED);
+        DrawRectanglePro(thirdRectangle, origin, rotation + 45.0f, BLUE);
+
+        EndMode2D();
+
+        EndTextureMode();
+
+        BeginMode2D(screenSpaceCamera);
+
+        // Draw the render texture with an offset of 1 worldSpace unit/pixel, so that the content behind the renderTexture is not shown.
+        // Also the renderTexture's height is flipped (in the source Rectangle), due to OpenGL reasons.
+        DrawTexturePro(
+            renderTexture.texture,
+            { 0.0f, 0.0f, (float)renderTexture.texture.width, (float)-renderTexture.texture.height },
+            { -virtualRatio, -virtualRatio, screenWidth + (virtualRatio * 2), screenHeight + (virtualRatio * 2) },
+            { 0.0f, 0.0f },
+            0.0f,
+            WHITE
+        );
+
+        EndMode2D();
+
+        DrawText("Screen resolution: 800x450", 5, 0, 20, DARKBLUE);
+        DrawText("World resolution: 160x90", 5, 20, 20, DARKGREEN);
+
+        EndDrawing();
+        //----------------------------------------------------------------------------------
+    }
+
+    // De-Initialization
+    //--------------------------------------------------------------------------------------
+
+    UnloadRenderTexture(renderTexture); // RenderTexture unloading
+
+    CloseWindow();        // Close window and OpenGL context
+    //--------------------------------------------------------------------------------------
+
+    return 0;
+}