note to myself

foobar.c

 struct {
		float z;
		uint32_t zs;
	} *pixels;
	int i;
	pixels = calloc(w * h, 8);
	glGetTextureImage(vkgl_depth_tex, 0,
			GL_DEPTH_STENCIL, GL_FLOAT_32_UNSIGNED_INT_24_8_REV,
			w * h * 8,
			pixels);

	FILE *fp;
	fp = fopen("foobar.txt", "wb");
	for (i = 0; i < w * h; i++) {
		fprintf(fp, "%f %u\n", pixels[i].z, (unsigned int)pixels[i].zs);
	}
	fclose(fp); 

└─ $ ▶ cat foobar.txt | awk '{print $2}' | sort | uniq 
└─ $ ▶ cat foobar.txt | awk '{print $1}' | sort | uniq