Come tagliare un'immagine/tela HTML a metà tramite javascript?

Question

Sto utilizzando html2canvas per trasformare un'API javascript di google map con funzioni personalizzate, in una tela e quindi un'immagine.

Funziona bene su tutti i browser, tranne che su IE 11 genera un'immagine con spazio in più a destra dell'immagine, uguale alla (larghezza della finestra del browser - larghezza della mappa). Quindi più ampia è la mia finestra, più spazio è a destra e viceversa.

Come posso tagliare questa immagine (o HTMLcanvas) esattamente al bordo dell'immagine reale (768px di larghezza)?

ho trovato questo codice qui, ma non sapevano come modificarlo per questo compito:

var image = new Image(); 
image.onload = cutImageUp; 
image.src = 'myimage.png'; 

function cutImageUp() { 
    var imagePieces = []; 
    for(var x = 0; x < numColsToCut; ++x) { 
     for(var y = 0; y < numRowsToCut; ++y) { 
      var canvas = document.createElement('canvas'); 
      canvas.width = widthOfOnePiece; 
      canvas.height = heightOfOnePiece; 
      var context = canvas.getContext('2d'); 
      context.drawImage(image, x * widthOfOnePiece, y * heightOfOnePiece, widthOfOnePiece, heightOfOnePiece, 0, 0, canvas.width, canvas.height); 
      imagePieces.push(canvas.toDataURL()); 
     } 
    } 

    // imagePieces now contains data urls of all the pieces of the image 

    // load one piece onto the page 
    var anImageElement = document.getElementById('myImageElementInTheDom'); 
    anImageElement.src = imagePieces[0]; 
} 

Answer 1

Ecco un fiasco tela che crea un'immagine. Avrai bisogno di regolare le dimensioni del ritaglio per la tua mappa.

// initialize the test canvas and wireup cut button. 
 
(function() { 
 
    var can = document.getElementById('test'); 
 
    var w = can.width = 400; 
 
    var h = can.height = 200; 
 
    var ctx = can.getContext('2d'); 
 

 
    ctx.fillStyle = "#336699"; 
 
    ctx.fillRect(0, 0, 200, 200); 
 
    ctx.strokeStyle = "#000000"; 
 
    ctx.lineWidth = 20; 
 
    ctx.strokeRect(0, 0, w, h); 
 
    ctx.strokeRect(0, 0, w/2, h); 
 
    var btn = document.getElementById('cut'); 
 
    btn.addEventListener('click', function() { 
 
     
 
    var croppedCan = crop(can, {x: 0, y: 0}, {x: 200, y: 200}); 
 
    
 
    // Create an image for the new canvas. 
 
    var image = new Image(); 
 
    image.src = croppedCan.toDataURL(); 
 
    
 
    // Put the image where you need to. 
 
    document.getElementsByTagName('body')[0].appendChild(image); 
 
    return image; 
 
    
 
    }); 
 
})(); 
 

 

 
// function crop 
 
// Returns a cropped canvas given a cavnas and crop region. 
 
// 
 
// Inputs: 
 
// can, canvas 
 
// a, {x: number, y: number} - left top corner 
 
// b, {x: number, y: number} - bottom right corner 
 

 
function crop(can, a, b) { 
 
    // get your canvas and a context for it 
 
    var ctx = can.getContext('2d'); 
 
    
 
    // get the image data you want to keep. 
 
    var imageData = ctx.getImageData(a.x, a.y, b.x, b.y); 
 
    
 
    // create a new cavnas same as clipped size and a context 
 
    var newCan = document.createElement('canvas'); 
 
    newCan.width = b.x - a.x; 
 
    newCan.height = b.y - a.y; 
 
    var newCtx = newCan.getContext('2d'); 
 
    
 
    // put the clipped image on the new canvas. 
 
    newCtx.putImageData(imageData, 0, 0); 
 
    
 
    return newCan;  
 
}

<button id='cut'>Crop</button> 
 
<hr/> 
 
<canvas id='test'></canvas> 
 
<hr/>

Answer 2

Ecco il codice che ho fatto, che prende la mappa di google, genera una tela, fette di esso al bordo dell'immagine reale per risolvere il bug di IE 11, poi uscite nuova immagine, e infine stampa il contenitore.

// Insert map container for output to printer 
    var element = $("#map-container"); 
    var printContainer = $("#printContainer"); 

    html2canvas(element, { 
     useCORS: true, 
     onrendered: function (canvas) { 

      // Must clear the printContainer before each session prints, or it will also print the previous info (if user presses the print results button twice) 
      printContainer.empty(); 

      // Put the map into a canvas inside #printContainer 
      printContainer.append(canvas); 

      // Find the canvas we just made 
      var myCanvas = printContainer.find("canvas")[0]; // add the [0] to get the native DOM element object 
      myCanvas.id = 'generatedCanvas1'; 

      // Check if we're running IE 11 or earlier 
      var ua = window.navigator.userAgent; 
      var isIE = (ua.indexOf('MSIE') > 0 || ua.indexOf('Trident') > 0); 

      if (isIE) { 
       console.log("We're on IE"); 

       // ========================================================================================== 
       // ======= IE Fix for canvas/image generation - slice the canvas ========================== 
       // ========================================================================================== 


       // function crop 
       // Returns a cropped canvas given a cavnas and crop region. 
       // 
       // Inputs: 
       // can, canvas 
       // a, {x: number, y: number} - left top corner 
       // b, {x: number, y: number} - bottom right corner 


       (function() { 
        var croppedCan = crop(myCanvas, { x: 0, y: 0 }, { x: 800, y: 768 }); 

        // Create an image for the new canvas. 
        var image = new Image(); 
        image.src = croppedCan.toDataURL(); 


        // Should we print the map image? Only if this is true... 
        if ($('*').hasClass('map-invisible posrel map-show')) { 

         //var dataUrl = canvas.toDataURL("image/png"); 

         imageMap = '<p style="text-align:center;"><img id="canvasImage" src="' + image.src + '" height="800" width="768" /></p>'; 
         div.append('<p>&nbsp;</p>').html(); 
         div.append(imageMap); 
        } 

        // Put the image where you need to. 
        //document.getElementById('printContainer').appendChild(image); 
        return image; 

        //}); 
       })(); 


       function crop(can, a, b) { 
        // get your canvas and a context for it 
        var ctx = can.getContext('2d'); 

        // get the image data you want to keep. 
        var imageData = ctx.getImageData(a.x, a.y, b.x, b.y); 

        // create a new cavnas same as clipped size and a context 
        var newCan = document.createElement('canvas'); 
        newCan.width = b.x - a.x; 
        newCan.height = b.y - a.y; 
        var newCtx = newCan.getContext('2d'); 

        // put the clipped image on the new canvas. 
        newCtx.putImageData(imageData, 0, 0); 

        return newCan; 
       } 


       // ========================================================================================== 
       // ======= END IE Fix for canvas/image generation - slice the canvas ====================== 
       // ========================================================================================== 
      } else { 
       console.log("We're not on IE"); 
       // For all other browsers except IE 

       // Should we print the map image? Only if this is true... 
       if ($('*').hasClass('map-invisible posrel map-show')) { 

        var image = new Image(); 
        image.src = canvas.toDataURL("image/png"); 

        imageMap = '<p style="text-align:center;"><img id="canvasImage" src="' + image.src + '" height="800" width="768" /></p>'; 
        div.append('<p>&nbsp;</p>').html(); 
        div.append(imageMap); 
       } 
      } 


      // Build the data set 
      div.append(criteriaDiv); 
      div.append(pageTable).html(); 


      // Add the new data into the hidden printContainer 
      printContainer.append(div); 

      // Remove the original canvas which was cropped so it doesnt print with the new canvas image 
      $("#generatedCanvas1").remove(); 

      // Fire the print command 
      printContainer.printThis({ 
       //debug: true 
       printDelay: 1500   // variable print delay needed so that css has time to load for the printout 

      }); 


      // For Debugging with the "#printMe" button 
      $(function() { 
       $("#printMe").click(function() { 
        //$printIframe.printThis({ 
        // debug: true, 
        printDelay: 1500   // variable print delay 

        //}); 
        var $iframe = $("iframe[name='printIframe']"); 


        setTimeout(function() { 
         if ($iframe.hasClass("MSIE")) { 
          // check if the iframe was created with the ugly hack 
          // and perform another ugly hack out of neccessity 
          window.frames["printIframe"].focus(); 
          $head.append("<script> window.print(); </script>"); 
         } else { 
          // proper method 
          if (document.queryCommandSupported("print")) { 
           $iframe[0].contentWindow.document.execCommand("print", false, null); 
          } else { 
           $iframe[0].contentWindow.focus(); 
           $iframe[0].contentWindow.print(); 
          } 
         } 


        }, 333); 
       }); 
      }); 

      // PrintThis usage and options 
      //* $("#mySelector").printThis({ 
      //*  debug: false,    * show the iframe for debugging 
      //*  importCSS: true,   * import page CSS 
      //*  importStyle: false,   * import style tags 
      //*  printContainer: true,  * grab outer container as well as the contents of the selector 
      //*  loadCSS: "path/to/my.css", * path to additional css file - us an array [] for multiple 
      //*  pageTitle: "",    * add title to print page 
      //*  removeInline: false,  * remove all inline styles from print elements 
      //*  printDelay: 333,   * variable print delay 
      //*  header: null,    * prefix to html 
      //*  formValues: true   * preserve input/form values 
      //* }); 
     } 
    }); 

Answer 3

tenta di utilizzare haxcv semplice libreria e facile

https://docs.haxcv.org/Methods/cutImage

esempio:.

var Pixel = _ ("img") cutImage (x, y, larghezza, altezza) ;

_ ("img"). Src (Pixels.src);