implement export cube faces

src/rtt.h

@@ -1,4 +1,5 @@
 #pragma once
+#include "image.h"
 
 class RTT
 {
@@ -28,20 +29,21 @@ public:
     bool recreate() { return create(w, h); }
     void clear(glm::vec4 color = glm::vec4(0));
     void clear_mask(glm::bool4 mask, glm::vec4 color = glm::vec4(0));
-    glm::ivec4 calc_bounds();
-    uint8_t* readTextureData(uint8_t* buffer = nullptr);
-    float* readTextureDataFloat(float* buffer = nullptr);
-    uint8_t* createBuffer();
-    float* createBufferFloat();
+    glm::ivec4 calc_bounds() const noexcept;
+    uint8_t* readTextureData(uint8_t* buffer = nullptr) const noexcept;
+    float* readTextureDataFloat(float* buffer = nullptr) const noexcept;
+    uint8_t* createBuffer() const noexcept;
+    float* createBufferFloat() const noexcept;
     void bindFramebuffer();
     void unbindFramebuffer();
     void bindTexture();
     void unbindTexture();
-    GLuint getTextureID() const { return texID; }
-    int getWidth() const { return w; }
-    int getHeight() const { return h; }
-    glm::ivec2 getSize() const { return { w, h }; }
-    int bytes() const { return w * h * 4; }
-    int stride() const { return w * 4; }
-    GLuint getFBO() const { return fboID; }
+    GLuint getTextureID() const noexcept { return texID; }
+    int getWidth() const noexcept { return w; }
+    int getHeight() const noexcept { return h; }
+    glm::ivec2 getSize() const noexcept { return { w, h }; }
+    int bytes() const noexcept { return w * h * 4; }
+    int stride() const noexcept { return w * 4; }
+    GLuint getFBO() const noexcept { return fboID; }
+    Image get_image() const noexcept;
 };