Question

I am trying to create a library i can use to handle 2d rendering in Opengl (c++) i have it all figured out except I can’t figure out how to set current colors transparent (ex. being able to set 255, 0, 255 to transparent) I realize from reading on the topic that I need to preprocess the texture and set that color’s alpha value to 0 but I have no idea how to do this.

PS: I am using SOIL for loading textures if that helps.

Answer 1

I realize from reading on the topic that I need to preprocess the texture and set that color’s alpha value to 0 but I have no idea how to do this.

for(y = 0; y < image.height; y++) for(x = 0; x < image.width; x++) {
    if( image.data[x, y].rgb == colorkey ) {
        image.data[x, y].alpha = 0.0;
    } else {
        image.data[x, y].alpha = 1.0;
    }
}

/* ... */

upload_image_to_texture(image);