+ glGetTexLevelParameteriv(target, level, GL_TEXTURE_WIDTH, width);
+ glGetTexLevelParameteriv(target, level, GL_TEXTURE_HEIGHT, height);
+
+ glBindTexture(target, bound_texture);
+
+ return *width > 0 && *height > 0;
+}
+
+
+static GLenum
+getTextureLevelFormat(GLint texture, GLint level)
+{
+ GLenum target;
+ GLint bound_texture = 0;
+ if (!bindTexture(texture, target, bound_texture)) {
+ return GL_NONE;
+ }
+
+ GLint format = GL_NONE;
+ glGetTexLevelParameteriv(target, level, GL_TEXTURE_INTERNAL_FORMAT, &format);
+
+ glBindTexture(target, bound_texture);
+
+ return format;
+}
+
+
+
+static bool
+getRenderbufferSize(GLint renderbuffer, GLint *width, GLint *height)
+{
+ GLint bound_renderbuffer = 0;
+ glGetIntegerv(GL_RENDERBUFFER_BINDING, &bound_renderbuffer);
+ glBindRenderbuffer(GL_RENDERBUFFER, renderbuffer);
+
+ *width = 0;
+ *height = 0;
+ glGetRenderbufferParameteriv(GL_RENDERBUFFER, GL_RENDERBUFFER_WIDTH, width);
+ glGetRenderbufferParameteriv(GL_RENDERBUFFER, GL_RENDERBUFFER_HEIGHT, height);
+
+ glBindRenderbuffer(GL_RENDERBUFFER, bound_renderbuffer);
+
+ return *width > 0 && *height > 0;
+}
+
+
+static GLenum
+getRenderbufferFormat(GLint renderbuffer)
+{
+ GLint bound_renderbuffer = 0;
+ glGetIntegerv(GL_RENDERBUFFER_BINDING, &bound_renderbuffer);
+ glBindRenderbuffer(GL_RENDERBUFFER, renderbuffer);
+
+ GLint format = GL_NONE;
+ glGetRenderbufferParameteriv(GL_RENDERBUFFER, GL_RENDERBUFFER_INTERNAL_FORMAT, &format);
+
+ glBindRenderbuffer(GL_RENDERBUFFER, bound_renderbuffer);
+
+ return format;
+}
+
+
+static bool
+getFramebufferAttachmentSize(GLenum target, GLenum attachment, GLint *width, GLint *height)
+{
+ GLint object_type = GL_NONE;
+ glGetFramebufferAttachmentParameteriv(target, attachment,
+ GL_FRAMEBUFFER_ATTACHMENT_OBJECT_TYPE,
+ &object_type);
+ if (object_type == GL_NONE) {
+ return false;
+ }
+
+ GLint object_name = 0;
+ glGetFramebufferAttachmentParameteriv(target, attachment,
+ GL_FRAMEBUFFER_ATTACHMENT_OBJECT_NAME,
+ &object_name);
+ if (object_name == 0) {
+ return false;
+ }
+
+ if (object_type == GL_RENDERBUFFER) {
+ return getRenderbufferSize(object_name, width, height);
+ } else if (object_type == GL_TEXTURE) {
+ GLint texture_level = 0;
+ glGetFramebufferAttachmentParameteriv(target, attachment,
+ GL_FRAMEBUFFER_ATTACHMENT_TEXTURE_LEVEL,
+ &texture_level);
+ return getTextureLevelSize(object_name, texture_level, width, height);
+ } else {
+ std::cerr << "warning: unexpected GL_FRAMEBUFFER_ATTACHMENT_OBJECT_TYPE = " << object_type << "\n";
+ return false;
+ }
+}
+
+
+
+static GLint
+getFramebufferAttachmentFormat(GLenum target, GLenum attachment)
+{
+ GLint object_type = GL_NONE;
+ glGetFramebufferAttachmentParameteriv(target, attachment,
+ GL_FRAMEBUFFER_ATTACHMENT_OBJECT_TYPE,
+ &object_type);
+ if (object_type == GL_NONE) {
+ return GL_NONE;
+ }
+
+ GLint object_name = 0;
+ glGetFramebufferAttachmentParameteriv(target, attachment,
+ GL_FRAMEBUFFER_ATTACHMENT_OBJECT_NAME,
+ &object_name);
+ if (object_name == 0) {
+ return GL_NONE;
+ }
+
+ if (object_type == GL_RENDERBUFFER) {
+ return getRenderbufferFormat(object_name);
+ } else if (object_type == GL_TEXTURE) {
+ GLint texture_level = 0;
+ glGetFramebufferAttachmentParameteriv(target, attachment,
+ GL_FRAMEBUFFER_ATTACHMENT_TEXTURE_LEVEL,
+ &texture_level);
+ return getTextureLevelFormat(object_name, texture_level);
+ } else {
+ std::cerr << "warning: unexpected GL_FRAMEBUFFER_ATTACHMENT_OBJECT_TYPE = " << object_type << "\n";
+ return GL_NONE;
+ }
+}
+
+
+
+image::Image *
+getDrawBufferImage() {
+ GLenum format = GL_RGB;
+ GLint channels = __gl_format_channels(format);
+ if (channels > 4) {