Texture.cpp

#include"Texture.h"

Texture::Texture(const char* image, const char* texType, GLuint slot)
{
	// Assigns the type of the texture to the texture object
	type = texType;
	// Generates an OpenGL texture object
	int widthImg, heightImg, numColCh;
	// Flips the image so it appears right side up
	stbi_set_flip_vertically_on_load(true);
	// Reads the image from a file and stores it in an array of bytes
	unsigned char* bytes = stbi_load(image, &widthImg, &heightImg, &numColCh, 0);

	// Creates the texture object
	glGenTextures(1, &ID);
	// Assigns the texture to a Texture Unit
	glActiveTexture(GL_TEXTURE0 + slot);
	unit = slot;
	// Binds the texture to the texture object
	glBindTexture(GL_TEXTURE_2D, ID);

	// Configures the type of algorithm that is used to make the image smaller or bigger
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);

	// Configures the way the texture repeats (if it does at all)
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
	// Note that GL_CLAMP_TO_EDGE is not supported in OpenGL ES 2.0
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);

	if (numColCh == 4)
		glTexImage2D
		(
			GL_TEXTURE_2D,
			0,
			GL_RGBA,
			widthImg,
			heightImg,
			0,
			GL_RGBA,
			GL_UNSIGNED_BYTE,
			bytes
		);
	else if (numColCh == 3)
		glTexImage2D
		(
			GL_TEXTURE_2D,
			0,
			GL_RGBA,
			widthImg,
			heightImg,
			0,
			GL_RGB,
			GL_UNSIGNED_BYTE,
			bytes
		);
	else if (numColCh == 1)
		glTexImage2D
		(
			GL_TEXTURE_2D,
			0,
			GL_RGBA,
			widthImg,
			heightImg,
			0,
			GL_RED,
			GL_UNSIGNED_BYTE,
			bytes
		);
	else
		throw std::invalid_argument("Automatic Texture type recognition failed. Only 1, 3 or 4 channels are supported.");

	// Generates MipMaps
	glGenerateMipmap(GL_TEXTURE_2D);

	// Deletes the image data as it is now stored in the OpenGL texture object
	stbi_image_free(bytes);
	// Unbinds the texture so that other textures can be used
	glBindTexture(GL_TEXTURE_2D, 0);
}

void Texture::texUnit(Shader& shader, const char* uniform, GLuint unit)
{
	GLuint texUni = glGetUniformLocation(shader.ID, uniform);
	shader.Activate();
	glUniform1i(texUni, unit);
}

void Texture::Bind()
{
	glActiveTexture(GL_TEXTURE0 + unit);
	glBindTexture(GL_TEXTURE_2D, ID);
}

void Texture::Unbind()
{
	glBindTexture(GL_TEXTURE_2D, 0);
}

void Texture::Delete()
{
	glDeleteTextures(1, &ID);
}