裁剪图像时，新图像获取canvas padding fabric js

Posted 2023-03-25

【中文标题】裁剪图像时，新图像获取canvas padding fabric js

【英文标题】：When image is cropped, the new image gets the canvas padding fabric js

【发布时间】：2021-07-08 13:00:18

【问题描述】：

首先，查看显示问题的视频 https://drive.google.com/file/d/1vcJC4qKToIbGeSQ0WNlJuAuWcT0rBeVZ/view

github 仓库链接https://github.com/alvaropsouza/web-image-editor

裁剪功能运行良好，它可以精确裁剪所选区域。真正的问题是，当创建裁剪的图像时，它会以某种方式获取画布填充，使用户更难找到图像边框来缩放、调整大小等......

PS：将新的图像填充设置为零将不起作用...此外，当我尝试更改它的宽度和高度功能时，裁剪无法正常工作，就像选择错误一样

裁剪函数脚本

var lastSelectedPicture = null;
var isInsertingCropRectangle = false;


var crop_rect, isDown, origX, origY, mask, target;
var done = false;

// IMAGEM DE PLANO DE FUNDO
var src = "https://i.imgur.com/nnCUr4g.jpg";
fabric.Image.fromURL(src, function(img) 
  img.dirty = true;
  img.selectable = false;
  canvas.add(img);
  canvas.renderAll();

canvas.setBackgroundImage(img, canvas.renderAll.bind(canvas), 
  scaleX: canvas.width / img.width,
  scaleY: canvas.height / img.height
)
);

// IMAGEM A SER RECORTADA
fabric.Image.fromURL(src, function(img) 
  img.selectable = true;
  img.id = 'target';
  img.borderColor = 'red'
  
  img.scaleX = canvas.width / img.width
  img.scaleY = canvas.height / img.height
  img.objectCaching = true,
  img.statefullCache = true,
  canvas.add(img);
  canvas.renderAll();
)

canvas.on('object:added', function(e) 
  target = null;
  mask = null;
  canvas.forEachObject(function(obj) 
    //alert(obj.get('id'));
    var id = obj.get('id');
    if (id === 'target') 
      target = obj;
       canvas.setActiveObject(obj);
   
    if (id === 'mask') 
      //alert(done);
      //alert('mask');
      mask = obj;
    
  );
);

canvas.on('object:modified', function(e) 
  e.target.setCoords();
  canvas.renderAll();
);

//////////////////////////////////////////////////////////
// MASK
//////////////////////////////////////////////////////////
document.getElementById("mask").addEventListener("click", function() 
    isInsertingCropRectangle = true;
        canvas.discardActiveObject();
        lastSelectedPicture.selectable = false;
        lastSelectedPicture.setCoords();
        lastSelectedPicture.dirty = true;
        canvas.renderAll();
        canvas.discardActiveObject();
        isInsertingCropRectangle = true;
);

//////////////////////////////////////////////////////////
// CROP
//////////////////////////////////////////////////////////
document.getElementById("crop").addEventListener("click", function() 
  if (target !== null && mask !== null) 
    console.log(mask, '01')
    console.log(crop_rect, '02')
        // Re-scale mask
    mask = rescaleMask(target, mask);
    mask.setCoords();
    // Do the crop
    target.clipPath = mask;
    
    target.dirty=true;
    canvas.setActiveObject(target);
    canvas.bringToFront(target);
    target.selectable = true;
    canvas.remove(mask)
    canvas.renderAll();
  
);

//////////////////////////////////////////////////////////
// RE-SCALE MASK FOR CROPPING
//////////////////////////////////////////////////////////
function rescaleMask(target, mask)
  mask.scaleX = 1;
  mask.scaleY = 1;

  mask.scaleX/=target.scaleX;
  mask.scaleY/=target.scaleY;
 
  var targetCenterX = target.width * target.scaleX / 2;
    var targetCenterY = target.height * target.scaleY / 2;

  var maskOverlapX = mask.left  - target.left;
  var maskOverlapY = mask.top - target.top;
    var centerBasedX = maskOverlapX - targetCenterX;
    var centerBasedY = maskOverlapY - targetCenterY;

  if( maskOverlapX >= targetCenterX)
    centerBasedX = (maskOverlapX - targetCenterX)/target.scaleX;
  
  else
 
    centerBasedX = (-(targetCenterX) + maskOverlapX)/target.scaleX;
  

  if( maskOverlapY >= targetCenterY)
    centerBasedY = (maskOverlapY - targetCenterY)/target.scaleY;
  
  else
    centerBasedY = (-(targetCenterY) + maskOverlapY)/target.scaleY;
  

  mask.left = centerBasedX;
  mask.top = centerBasedY;
  mask.originX = 'left';
  mask.originY = 'top';
  mask.setCoords();
  mask.dirty=true;
  canvas.renderAll();
  
  //var newMask = mask;
  return mask;


canvas.on('mouse:down', function(o) 
    if( isInsertingCropRectangle == true )
    if (done) 
      canvas.renderAll();
      return;
    
    isDown = true;
    var pointer = canvas.getPointer(o.e);
    origX = pointer.x;
    origY = pointer.y;
    crop_rect = new fabric.Rect(
      left: origX,
      top: origY,
      width: pointer.x - origX,
      height: pointer.y - origY,
      opacity: .3,
      transparentCorners: false,
      selectable: true,
      id: 'mask',
      borderColor: 'red'
    );
    canvas.add(crop_rect);
    canvas.renderAll();
  
);

canvas.on('mouse:move', function(o) 
    if( isInsertingCropRectangle == true )
    if (done) 
      canvas.renderAll();
      return;
    
    if (!isDown) return;
    var pointer = canvas.getPointer(o.e);

    if (origX > pointer.x) 
      crop_rect.set(
        left: Math.abs(pointer.x)
      );
    
    if (origY > pointer.y) 
      crop_rect.set(
        top: Math.abs(pointer.y)
      );
    

    crop_rect.set(
      width: Math.abs(origX - pointer.x)
    );
    crop_rect.set(
      height: Math.abs(origY - pointer.y)
    );


    crop_rect.setCoords();
    canvas.renderAll();
  
  else
  
  
);

canvas.on('mouse:up', function(o) 
    if( isInsertingCropRectangle == true )
    if (done) 
      canvas.renderAll();
      return;
    
    isDown = false;

    crop_rect.set(
      selectable: true
    );
    done = true;
  
  else
  
  
);

    canvas.on('selection:created', function(event) 
        selectionChanged(event);
  );
    
    canvas.on('selection:updated', function(event) 
        selectionChanged(event);
    );

    function selectionChanged(event)
    switch(event.target.type) 
      case 'textbox':
        break;
        case 'image':
          lastSelectedPicture = event.target;
                break;
            case 'rect':
                break;
            case 'group':
                break;
            default:
                break;
        
        
    

【参考方案1】：

您当前正在使用 clipPaths 裁剪图像，该图像始终保持原始对象的尺寸，而不是 clipPath 的尺寸（请参阅http://fabricjs.com/clippath-part1）。尝试使用图像属性width、height、cropX 和cropY 来实现裁剪效果，这将使图像的边界框具有正确的尺寸。

img.set( width:100, height:100, cropX: 50, cropY: 50 );