我正在使用 ImGUI 为图像创建颜色选择器 OpenGL 应用程序。我设法通过将图像加载到 aglTexImage2D
并使用ImGUI::Image()
. 现在我想实现一个方法,它可以在鼠标左键单击的情况下确定像素的颜色。
这是我加载纹理,然后将其分配给帧缓冲区的方法:
bool LoadTextureFromFile(const char *filename, GLuint *out_texture, int *out_width, int *out_height,ImVec2 mousePosition ) {
// Reading the image into a GL_TEXTURE_2D
int image_width = 0;
int image_height = 0;
unsigned char *image_data = stbi_load(filename, &image_width, &image_height, NULL, 4);
if (image_data == NULL)
return false;
GLuint image_texture;
glGenTextures(1, &image_texture);
glBindTexture(GL_TEXTURE_2D, image_texture);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, image_width, image_height, 0, GL_RGBA, GL_UNSIGNED_BYTE, image_data);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
stbi_image_free(image_data);
glBindTexture(GL_TEXTURE_2D, 0);
*out_texture = image_texture;
*out_width = image_width;
*out_height = image_height;
// Assigning texture to Frame Buffer
unsigned int fbo;
glGenFramebuffers(1, &fbo);
glBindFramebuffer(GL_FRAMEBUFFER, fbo);
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, image_texture, 0); glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, image_texture, 0);
if(glCheckFramebufferStatus(GL_FRAMEBUFFER) == GL_FRAMEBUFFER_COMPLETE){
std::cout<< "Frame buffer is done."<< std::endl;
}
return true;
}
不幸的是,上面的代码导致一个完全空白的屏幕。我想,在设置帧缓冲区时我错过了一些东西。
这是方法,我想使用鼠标坐标对帧缓冲区纹理进行采样:
void readPixelFromImage(ImVec2 mousePosition) {
unsigned char pixels[4];
glReadBuffer(GL_COLOR_ATTACHMENT0);
glReadPixels(GLint(mousePosition.x), GLint(mousePosition.y), 1, 1, GL_RGBA, GL_UNSIGNED_BYTE, pixels);
std::cout << "r: " << static_cast<int>(pixels[0]) << '\n';
std::cout << "g: " << static_cast<int>(pixels[1]) << '\n';
std::cout << "b: " << static_cast<int>(pixels[2]) << '\n';
std::cout << "a: " << static_cast<int>(pixels[3]) << '\n' << std::endl;
}
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