I am writing an openGl wrapper in rust for educational purposes. However, I have a problem displaying textures from an image file (jpg). The image is displayed as a grayscale image with some buggy red and green lines.
I am loading the image using the "image" crate and converting it to a ImageBuffer. The loading part is working, what i have checked by saving the image again.
I think that the conversion of the buffer to rgb is also working because the second time i save the image it is also working.
code to load the image:
extern crate image;
use gl;
use std::{path, ffi::c_void};
#[derive(Debug)]
pub struct Texture {
id: u32,
location: gl::types::GLenum,
path: path::PathBuf,
}
enum TextureError {
FileNotFound(path::PathBuf),
InvalidFileType(String)
}
impl Texture {
pub fn new(file_path: &str, location: u32) -> Texture {
let mut id = 0;
let img = image::open(file_path).unwrap();
img.save("res/test.jpg").unwrap();
let img = match img {
image::DynamicImage::ImageRgb8(img) => img,
x => x.to_rgb8()
};
let width = img.width();
let height = img.height();
img.save("res/test2.jpg").unwrap();
unsafe {
gl::ActiveTexture(gl::TEXTURE0 + location);
gl::GenTextures(1, &mut id);
gl::BindTexture(gl::TEXTURE_2D, id);
gl::TexParameteri(gl::TEXTURE_2D, gl::TEXTURE_WRAP_S, gl::REPEAT as i32);
gl::TexParameteri(gl::TEXTURE_2D, gl::TEXTURE_WRAP_T, gl::REPEAT as i32);
gl::TexParameteri(gl::TEXTURE_2D, gl::TEXTURE_MIN_FILTER, gl::LINEAR_MIPMAP_LINEAR as i32);
gl::TexParameteri(gl::TEXTURE_2D, gl::TEXTURE_MAG_FILTER, gl::LINEAR as i32);
gl::TexImage2D(gl::TEXTURE_2D, 0, gl::RGB8 as i32, width as i32, height as i32, 0, gl::RGB, gl::UNSIGNED_BYTE, (&img as &[u8]).as_ptr() as *const c_void);
gl::GenerateMipmap(gl::TEXTURE_2D);
}
Texture {
id,
location,
path: path::PathBuf::from(file_path)
}
}
}
main code:
The modules fundamental, shader, window, etc. are modules i wrote and tested. (they work as inteded)
extern crate gl;
extern crate glfw;
#[macro_use]
extern crate lazy_static;
mod fundamental;
mod shader;
mod window;
use window::Window;
use crate::fundamental::{Buffer, VertexArray, VertexAttribPtr, Texture};
fn main() {
//setup glfw
let mut window = Window::new();
//load OpenGL
gl::load_with(|s| window.glfw_window.get_proc_address(s) as *const _);
unsafe {
gl::Viewport(0, 0, 600, 600);
}
let vertices: Vec<f32> = vec![
-0.5, -0.5, 0.0, 0.0, 0.0,
0.5, -0.5, 0.0, 1.0, 0.0,
-0.5, 0.5, 0.0, 0.0, 1.0,
0.5, 0.5, 0.0, 1.0, 1.0
];
let indices: Vec<u32> = vec![0, 1, 2, 1, 2, 3];
let vao = VertexArray::new();
vao.bind();
let vbo = Buffer::new(gl::STATIC_DRAW, gl::ARRAY_BUFFER);
let ebo = Buffer::new(gl::STATIC_DRAW, gl::ELEMENT_ARRAY_BUFFER);
vbo.set_data(&vertices);
ebo.set_data(&indices);
let _v_a_ptr0 = VertexAttribPtr::new(0, 3, gl::FLOAT, 5 * 4, 0);
let _v_a_ptr1 = VertexAttribPtr::new(1, 2, gl::FLOAT, 5 * 4, 3 * 4);
vao.unbind();
let shader = shader::Shader::new("shaders/shader.vs", "shaders/shader.fs", None);
let _texture_bonfire = Texture::new("res/bonfire.jpg", 0);
//rendering loop
println!("---Starting rendering loop---");
while window.not_closed() {
window.poll_events();
unsafe {
gl::ClearColor(0.2, 0.3, 0.3, 1.0);
gl::Clear(gl::COLOR_BUFFER_BIT);
let mut error = gl::GetError();
while error != 0 {
println!("{}", error);
error = gl::GetError();
}
shader.bind();
vao.bind();
gl::DrawElements(
gl::TRIANGLES,
indices.len() as i32,
gl::UNSIGNED_INT,
std::ptr::null(),
);
}
window.swap_buffers();
}
}
the code of the vertex_attrib_ptr moule:
(just in case it is needed)
use std::ffi::c_void;
pub struct VertexAttribPtr {
location: u32,
}
impl VertexAttribPtr {
pub fn new(
location: u32,
size_of_attribute: i32,
vertex_type: gl::types::GLenum,
vertex_size: i32,
offset: u32,
) -> VertexAttribPtr {
unsafe {
gl::VertexAttribPointer(
location,
size_of_attribute,
vertex_type,
gl::FALSE,
vertex_size,
offset as *const c_void,
);
gl::EnableVertexAttribArray(location);
}
VertexAttribPtr { location }
}
#[allow(unused)]
pub fn enable(&self) {
unsafe {
gl::EnableVertexAttribArray(self.location);
}
}
#[allow(unused)]
pub fn disable(&self) {
unsafe {
gl::DisableVertexAttribArray(self.location);
}
}
}
vertex shader
#version 460 core
layout (location = 0) in vec3 pos;
layout (location = 1) in vec2 tex_coord;
out vec2 texture_cord;
void main()
{
gl_Position = vec4(pos.x, pos.y, pos.z, 1.0);
texture_cord = tex_coord;
}
fragment shader
#version 460 core
out vec4 FragColor;
in vec2 texture_cord;
uniform sampler2D texture0;
void main()
{
FragColor = texture(texture0, texture_cord);
//FragColor = vec4(1.0);
}
rendered texture:
The texture image is also upside down, but this is a problem for later.
original image
>Solution :
By default OpenGL assumes that the start of each row of an image is aligned to 4 bytes.
This is because the gl::UNPACK_ALIGNMENT parameter by default is 4. Since the image has 3 color channels (gl::RGB), and is tightly packed the size of a row of the image may not be aligned to 4 bytes.
When a RGB image with 3 color channels is loaded to a texture object and 3*width is not divisible by 4, gl::UNPACK_ALIGNMENT has to be set to 1, before specifying the texture image with gl::TexImage2D:
gl::PixelStorei(gl::UNPACK_ALIGNMENT, 1);
gl::TexImage2D(gl::TEXTURE_2D, 0, gl::RGB8 as i32, width as i32, height as i32, 0, gl::RGB, gl::UNSIGNED_BYTE, (&img as &[u8]).as_ptr() as *const c_void);
The texture is also flipped. You have to "swap" the 2nd component of the texture coordinates:
let vertices: Vec<f32> = vec![
-0.5, -0.5, 0.0, 0.0, 1.0,
0.5, -0.5, 0.0, 1.0, 1.0,
-0.5, 0.5, 0.0, 0.0, 0.0,
0.5, 0.5, 0.0, 1.0, 0.0
];