Unity - How To crop 2D sprite in Unity 2D and Unity 3D

In version 4.3 and later, Unity introduces new 2D tools for 2D game play.

Step 1 Sprite

Sprite is one of the new functionality of 2D tools that is used in 2D games. Setting the texture importer of an image in project explorer can create sprite.

To create sprite, just drag and drop an image in assets folder and set Sprite Importer settings in inspector.

After creating sprite, it can be used as graphic in scene with the help of Sprite Renderer component.

Step 2 Sprite Renderer

Understand About Sprite Renderer:

• Sprite Renderer component is used to access or display the sprite in scene.

Some useful properties of 2D sprite renderer:

Step 3 Example

The following simple c# code will draw simple line rectangle on mouse move and crop the 2D sprite when mouse up.

3.1 Basic Setup

Add empty game object and put following script on it.

Create sprite as described above and add BoxCollider or BoxCollider2D component on it.

Rotation of sprite must be (0,0,0);.

Video:

3.2 CropSprite Script

using UnityEngine;
using System.Collections;
 
public class CropSprite : MonoBehaviour
{
// Reference for sprite which will be cropped and it has BoxCollider or BoxCollider2D
public GameObject spriteToCrop;
 
private Vector3 startPoint, endPoint;
private bool isMousePressed;
// For sides of rectangle. Rectangle that will display cropping area
private LineRenderer leftLine, rightLine, topLine, bottomLine;
 
void Start ()
{
isMousePressed = false;
// Instantiate rectangle sides
leftLine = createAndGetLine("LeftLine");
rightLine = createAndGetLine("RightLine");
topLine = createAndGetLine("TopLine");
bottomLine = createAndGetLine("BottomLine");
}
// Creates line through LineRenderer component
private LineRenderer createAndGetLine (string lineName)
{
GameObject lineObject = new GameObject(lineName);
LineRenderer line = lineObject.AddComponent();
line.SetWidth(0.03f,0.03f);
line.SetVertexCount(2);
return line;
}
void Update ()
{
if(Input.GetMouseButtonDown(0) && isSpriteTouched(spriteToCrop))
{
isMousePressed = true;
startPoint = Camera.main.ScreenToWorldPoint(Input.mousePosition);
}
else if(Input.GetMouseButtonUp(0))
{
if(isMousePressed)
cropSprite();	
isMousePressed = false;
}
if(isMousePressed && isSpriteTouched(spriteToCrop))
{
endPoint = Camera.main.ScreenToWorldPoint(Input.mousePosition);
drawRectangle();
}
}
// Following method draws rectangle that displays cropping area
private void drawRectangle()
{
leftLine.SetPosition(0, new Vector3(startPoint.x, endPoint.y, 0));
leftLine.SetPosition(1, new Vector3(startPoint.x, startPoint.y, 0));
 
rightLine.SetPosition(0, new Vector3(endPoint.x, endPoint.y, 0));
rightLine.SetPosition(1, new Vector3(endPoint.x, startPoint.y, 0));
 
topLine.SetPosition(0, new Vector3(startPoint.x, startPoint.y, 0));
topLine.SetPosition(1, new Vector3(endPoint.x, startPoint.y, 0));
 
bottomLine.SetPosition(0, new Vector3(startPoint.x, endPoint.y, 0));
bottomLine.SetPosition(1, new Vector3(endPoint.x, endPoint.y, 0));
}
// Following method crops as per displayed cropping area
private void cropSprite()
{
// Calculate topLeftPoint and bottomRightPoint of drawn rectangle
Vector3 topLeftPoint = startPoint, bottomRightPoint=endPoint;
if((startPoint.x > endPoint.x))
{
topLeftPoint = endPoint;
bottomRightPoint = startPoint;
}
if(bottomRightPoint.y > topLeftPoint.y)
{
float y = topLeftPoint.y;
topLeftPoint.y = bottomRightPoint.y;
bottomRightPoint.y = y;
}
 
SpriteRenderer spriteRenderer = spriteToCrop.GetComponent();
Sprite spriteToCropSprite = spriteRenderer.sprite;
Texture2D spriteTexture = spriteToCropSprite.texture;
Rect spriteRect = spriteToCrop.GetComponent().sprite.textureRect;
 
int pixelsToUnits = 100; // It's PixelsToUnits of sprite which would be cropped
 
// Crop sprite
 
GameObject croppedSpriteObj = new GameObject("CroppedSprite");
Rect croppedSpriteRect = spriteRect;
croppedSpriteRect.width = (Mathf.Abs(bottomRightPoint.x - topLeftPoint.x)*pixelsToUnits)* (1/spriteToCrop.transform.localScale.x);
croppedSpriteRect.x = (Mathf.Abs(topLeftPoint.x - (spriteRenderer.bounds.center.x-spriteRenderer.bounds.size.x/2)) *pixelsToUnits)* (1/spriteToCrop.transform.localScale.x);
croppedSpriteRect.height = (Mathf.Abs(bottomRightPoint.y - topLeftPoint.y)*pixelsToUnits)* (1/spriteToCrop.transform.localScale.y);
croppedSpriteRect.y = ((topLeftPoint.y - (spriteRenderer.bounds.center.y - spriteRenderer.bounds.size.y/2))*(1/spriteToCrop.transform.localScale.y))* pixelsToUnits - croppedSpriteRect.height;//*(spriteToCrop.transform.localScale.y);
Sprite croppedSprite = Sprite.Create(spriteTexture, croppedSpriteRect, new Vector2(0,1), pixelsToUnits);
SpriteRenderer cropSpriteRenderer = croppedSpriteObj.AddComponent();	
cropSpriteRenderer.sprite = croppedSprite;
topLeftPoint.z = -1;
croppedSpriteObj.transform.position = topLeftPoint;
croppedSpriteObj.transform.parent = spriteToCrop.transform.parent;
croppedSpriteObj.transform.localScale = spriteToCrop.transform.localScale;
Destroy(spriteToCrop);
}
 
// Following method checks whether sprite is touched or not. There are two methods for simple collider and 2DColliders. you can use as per requirement and comment another one.
 
// For simple 3DCollider
// private bool isSpriteTouched(GameObject sprite)
// {
// RaycastHit hit;
// Ray ray = Camera.main.ScreenPointToRay (Input.mousePosition);
// if (Physics.Raycast (ray, out hit))
// {
// if (hit.collider != null && hit.collider.name.Equals (sprite.name))
// return true;
// }
// return false;
// }
 
// For 2DCollider
private bool isSpriteTouched(GameObject sprite)
{
Vector3 posFor2D = Camera.main.ScreenToWorldPoint(Input.mousePosition);
RaycastHit2D hit2D = Physics2D.Raycast(posFor2D, Vector2.zero);
if (hit2D != null && hit2D.collider != null)
{
if(hit2D.collider.name.Equals(sprite.name))
return true;
}
return false;
}
}

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