3dtrial/tinyrender3_homework/image.go

package main

import (
	"bytes"
	"fmt"
	"image/color"
	"math"
	"strings"
)

// Convert rgb to uint
func Col2Uint(r, g, b byte) uint {
	return (uint(r) << 16) | (uint(g) << 8) | uint(b)
}

func Color2Uint(col color.Color) uint {
	r, g, b, _ := col.RGBA()
	return uint((r << 16) | (g << 8) | b)
}

// Convert uint to rgb (in that order)
func Uint2Col(col uint) (byte, byte, byte) {
	return byte((col >> 16) & 0xFF), byte((col >> 8) & 0xFF), byte(col & 0xFF)
}

// Color is in ARGB (alpha not used right now)
type Framebuffer struct {
	Data    []uint
	ZBuffer []float32 //uint16 // Apparently 16 bit z-buffers are used
	Width   uint
	Height  uint
}

// Create a new framebuffer for the given width and height.
func NewFramebuffer(width uint, height uint) Framebuffer {
	return Framebuffer{
		Data:    make([]uint, width*height),
		ZBuffer: make([]float32, width*height),
		Width:   width,
		Height:  height,
	}
}

// Fill zbuffer with pixels that are max distance away
func (fb *Framebuffer) ResetZBuffer() {
	for i := range fb.ZBuffer {
		fb.ZBuffer[i] = math.MaxFloat32
	}
}

// Sure hope this gets inlined...
func (fb *Framebuffer) Set(x uint, y uint, color uint) {
	fb.Data[x+y*fb.Width] = color
}

func (fb *Framebuffer) SetSafe(x uint, y uint, color uint) {
	if x >= fb.Width || y >= fb.Height {
		return
	}
	fb.Data[x+y*fb.Width] = color
}

// Given some image data, return a string that is the ppm of it
func (fb *Framebuffer) ExportPPM() string {
	var result strings.Builder
	result.WriteString(fmt.Sprintf("P3\n%d %d\n255\n", fb.Width, fb.Height))
	for y := range fb.Height {
		for x := range fb.Width {
			r, g, b := Uint2Col(fb.Data[x+y*fb.Width])
			result.WriteString(fmt.Sprintf("%d %d %d\t", r, g, b))
		}
		result.WriteRune('\n')
	}
	return result.String()
}

func (fb *Framebuffer) ExportPPMP6() []byte {
	var result bytes.Buffer
	result.WriteString(fmt.Sprintf("P6\n%d %d\n255\n", fb.Width, fb.Height))
	for i := range fb.Data {
		r, g, b := Uint2Col(fb.Data[i])
		result.Write([]byte{r, g, b})
		//result.WriteString(fmt.Sprintf("%d %d %d\t", r, g, b))
	}
	//result.WriteRune('\n')
	return result.Bytes()
}

func (fb *Framebuffer) ZBuffer_ExportPPM() string {
	var result strings.Builder
	mini := float32(math.MaxFloat32)
	maxi := float32(-math.MaxFloat32)
	for _, f := range fb.ZBuffer {
		if f == math.MaxFloat32 {
			continue
		}
		mini = min(f, mini)
		maxi = max(f, maxi)
	}
	result.WriteString(fmt.Sprintf("P2\n%d %d\n255\n", fb.Width, fb.Height))
	for y := range fb.Height {
		for x := range fb.Width {
			if fb.ZBuffer[x+y*fb.Width] == math.MaxFloat32 {
				result.WriteString("0 ")
			} else {
				zp := byte(math.Abs(float64(255 * fb.ZBuffer[x+y*fb.Width] / (maxi - mini))))
				result.WriteString(fmt.Sprintf("%d ", zp))
			}
		}
		result.WriteRune('\n')
	}
	return result.String()
}