Question

我们正在从JSON获取蒙版图像并在Container中显示

Onclick蒙版图像，我们允许如下在蒙版上上传另一个图像，用户也可以像在Codepen1中那样拖动该上传的图像，一切都很好...

现在客户端希望在Box图像上方显示遮罩图像，因此我在Box图像顶部显示了遮罩图像，如下所示：

问题：

当我单击蒙版图像[左侧]时，较高的z-index值分配给框图像，因此框图像将覆盖蒙版图像。因为蒙版图像和盒子图像彼此重叠。

当我单击蒙版图像[右侧]时，就没有问题...

此外，我可以成功地从蒙版图像的右侧拖动上传的图像，而不能从左侧拖动。

Z索引代码：

container.enable = function() {
    draggable = true;
    $(canvas).attr("active", "true");
    div.css({
        "z-index": 2
    });
}

container.disable = function() {
    draggable = false;
    $(canvas).attr("active", "false");
    div.css({
        "z-index": 1
    });
}

代码段：

var target;
const imageUrl = "";

let jsonData = {
    "layers": [{
        "name": "design3",
        "x": 0,
        "y": 0,
        "width": 300,
        "height": 300,
        "layers":[  
            {  
               "type":"image",
               "src":"14IVyVb.png",
               "name":"bg_img",
               "x":0,
               "y":0,
               "width":200,
               "height":200
            },
            {  
               "type":"image",
               "src":"l8vA9bB.png",
               "name":"mask_image",
               "x":100,
               "y":15,
               "width":180,
               "height":166            
        }]
    }]
};

const containerElement = $('#container');
const fileUp = $('#fileup');
let mask;

$(function() {

    // Upload image onclick mask image 

    containerElement.click(function(e) {
        var res = e.target;
        target = res.id;
        if (e.target.getContext) {
            // click only inside Non Transparent part 
            var pixel = e.target.getContext('2d').getImageData(e.offsetX, e.offsetY, 1, 1).data;
            if (pixel[3] === 255) {
                setTimeout(() => {
                    $('#fileup').click();
                }, 20);
            }
        }
    });

    // Fetch mask images from json file - IGNORE this code 

    function getAllSrc(layers) {
        let arr = [];
        layers.forEach(layer => {
            if (layer.src) {
                arr.push({
                    src: layer.src,
                    x: layer.x,
                    y: layer.y,
                    height: layer.height,
                    width: layer.width,
                    name: layer.name
                });
            } else if (layer.layers) {
                let newArr = getAllSrc(layer.layers);
                if (newArr.length > 0) {
                    newArr.forEach(({
                        src,
                        x,
                        y,
                        height,
                        width,
                        name
                    }) => {
                        arr.push({
                            src,
                            x: (layer.x + x),
                            y: (layer.y + y),
                            height,
                            width,
                            name: (name)
                        });
                    });
                }
            }
        });
        return arr;
    }

    function json(data) {
        var width = 0;
        var height = 0;

        let arr = getAllSrc(data.layers);
        let layer1 = data.layers;
        width = layer1[0].width;
        height = layer1[0].height;
        let counter = 0;
        let table = [];

        // container dimensions 
        containerElement.css('width', width + "px").css('height', height + "px").addClass('temp');
        //end 

        for (let {
                src,
                x,
                y,
                name
            } of arr) {

            //Get Height and width of mask image [ edit button ] 
            var ImagePosition = arr;
            //code end 

            var imageUrl1 = imageUrl;

            var mask = $(".container").mask({
                imageUrl: name.indexOf('mask_') !== -1 ? imageUrl1 : undefined,

                // Fetch Mask images 
                maskImageUrl: 'http://i.imgur.com/' + src,
                // end 

                onMaskImageCreate: function(img) {
                    // Mask image positions 
                    img.css({
                        "position": "absolute",
                        "left": x + "px",
                        "top": y + "px"
                    });
                    // end 

                },
                id: counter
            });
            // here 

            ImagePosition.map(function(cur, index) {
                var available = cur.name.includes('mask_');

                if (!available) {
                    $('.masked-img' + index).css('pointer-events', 'none');
                }
            });

            table.push(mask);
            fileup.onchange = function() {

                let mask2 = table[target];
                const newImageLoadedId = mask2.loadImage(URL.createObjectURL(fileup.files[0]));
                document.getElementById('fileup').value = "";

            };
            counter++;
        }
        return mask;
    }
    mask = json(jsonData);
}); // end of function 

// Image code 

(function($) {
    window.JQmasks = [];
    $.fn.mask = function(options) {
        // This is the easiest way to have default options. 
        var settings = $.extend({
            // These are the defaults. 
            maskImageUrl: undefined,
            imageUrl: undefined,
            scale: 1,
            id: new Date().getUTCMilliseconds().toString(),
            x: 0, // image start position 
            y: 0, // image start position 
            onMaskImageCreate: function(div) {},
        }, options);

        // Create the image properties
        settings.maskImage = new Image
        settings.image = new Image

        // set the cross-origin attributes
        settings.maskImage.setAttribute('crossOrigin', 'anonymous');
        settings.image.setAttribute('crossOrigin', 'anonymous');

        settings.maskImage.onload = function() {
            // once the mask is loaded, load the image
            container.loadImage(settings.imageUrl)
            container.drawMask()
        }

        settings.image.onload = function() {
            // once the image is loaded, render to canvas

            container.drawImage()
        }

        var container = $(this);

        let prevX = 0,
            prevY = 0,
            draggable = false,
            img,
            canvas,
            context,
            image,
            timeout,
            initImage = false,
            startX = settings.x,
            startY = settings.y,
            div;

        container.mousePosition = function(event) {
            return {
                x: event.pageX || event.offsetX,
                y: event.pageY || event.offsetY
            };
        }


         container.selected = function(ev) {
            var pos = container.mousePosition(ev);
            var item = $(".masked-img canvas").filter(function() {
                var offset = $(this).offset()
                var x = pos.x - offset.left;
                var y = pos.y - offset.top;
                var d = this.getContext('2d').getImageData(x, y, 1, 1).data;
                return d[0] > 0
            });

            JQmasks.forEach(function(el) {
                var id = item.length > 0 ? $(item).attr("id") : "";
                if (el.id == id)
                    el.item.enable();
                else el.item.disable();
            });
        };

        container.enable = function() {
            draggable = true;
            $(canvas).attr("active", "true");
            div.css({
                "z-index": 2
            });
        }

        container.disable = function() {
            draggable = false;
            $(canvas).attr("active", "false");
            div.css({
                "z-index": 1
            });
        }      

        container.drawMask = function() {
            if (!settings.maskImage) return true;
            canvas.width = settings.maskImage.width;
            canvas.height = settings.maskImage.height;
            context.save();
            context.beginPath();
            context.globalCompositeOperation = "source-over";
            // draw the masked image after scaling 
            if (settings.maskImage) context.drawImage(settings.maskImage, 0, 0, settings.maskImage.width, settings.maskImage.height);
            context.restore()
        };

         container.drawImage = function() {
            const img = settings.image

            settings.x = settings.x == 0 && initImage ? (canvas.width - (img.width * settings.scale)) / 2 : settings.x;
            settings.y = settings.y == 0 && initImage ? (canvas.height - (img.height * settings.scale)) / 2 : settings.y;

            context.globalCompositeOperation = 'source-atop';
            context.save();
            context.translate(settings.x + img.width / 2, settings.y + img.height / 2);
            context.rotate(settings.rotate);
            context.scale(settings.scale, settings.scale);
            context.translate(-(settings.x + img.width / 2), -(settings.y + img.height / 2));
            let width = img.width,
                height = img.height;
            if (img)
                context.drawImage(img, settings.x, settings.y, width, height);
            context.restore();
            initImage = false;           
        }

        // change the draggable image 
		
		container.onDragStart = function(evt) {
            // console.log('Draw started');
            if (evt.target.getContext) {
                var pixel = evt.target.getContext('2d').getImageData(evt.offsetX, evt.offsetY, 1, 1).data;

                $(canvas).attr("active", "true");
                container.selected(evt);
                prevX = evt.clientX;
                prevY = evt.clientY;
                var img = new Image();
                evt.originalEvent.dataTransfer.setDragImage(img, 10, 10);
                evt.originalEvent.dataTransfer.setData('text/plain', 'anything');

            }
        };

        container.onDragOver = function(evt) {
            // console.log('Drag over');
            if (evt.target.getContext) {
                var pixel = evt.target.getContext('2d').getImageData(evt.offsetX, evt.offsetY, 1, 1).data;
                if (pixel[3] === 255) {
                    if (draggable && $(canvas).attr("active") === "true") {
                        var x = settings.x + evt.clientX - prevX;
                        var y = settings.y + evt.clientY - prevY;
                        if (x == settings.x && y == settings.y)
                            return; // position has not changed
                        settings.x += evt.clientX - prevX;
                        settings.y += evt.clientY - prevY;
                        prevX = evt.clientX;
                        prevY = evt.clientY;
                        //logTMatrix(settings);
                        clearTimeout(timeout);
                        timeout = setTimeout(function() {
                            container.drawMask();
                            container.drawImage();
                        }, 1);
                    }
                } else {
                    evt.stopPropagation();
                    return false;
                }
            }
        };


        container.loadImage = function(imageUrl) {
            if (!imageUrl) return true;
            settings.y = startY;
            settings.x = startX;
            prevX = prevY = 0;

            initImage = true;

            settings.image.src = imageUrl; // CHANGED

            // sirpepole Add this 
            return settings.id;
        };

        container.loadMaskImage = function(imageUrl, from) {

            canvas = document.createElement("canvas");
            context = canvas.getContext('2d');
            canvas.setAttribute("draggable", "true");
            canvas.setAttribute("id", settings.id);
            // settings.maskImageUrl = imageUrl;
            settings.maskImage.src = imageUrl // CHANGED

            div = $("<div/>", {
                "class": "masked-img"
            }).append(canvas);

            // div.find("canvas").on('touchstart mousedown', function(event) 
            div.find("canvas").on('dragstart', function(event) {
                if (event.handled === false) return;
                event.handled = true;
                container.onDragStart(event);
            });

            div.find("canvas").on('touchend mouseup', function(event) {
                if (event.handled === false) return;
                event.handled = true;
                container.selected(event);
            });

            div.find("canvas").bind("dragover", container.onDragOver);

            container.append(div);
            if (settings.onMaskImageCreate)
                settings.onMaskImageCreate(div);

            // container.loadImage(settings.imageUrl);
            // Moved this to the settings.maskImage.onload
        };
        if (settings.maskImageUrl) {
            container.loadMaskImage(settings.maskImageUrl);
        }
        JQmasks.push({
            item: container,
            id: settings.id
        })
        // Edit image 
        div.addClass('masked-img' + settings.id);
        div.attr('data-id', settings.id);
        // ends 
        return container;
    };
}(jQuery));

.container {
        background: silver;
        position: relative;
    }
    
    .container img {
        position: absolute;
        top: 0;
        bottom: 250px;
        left: 0;
        right: 0;
        margin: auto;
        z-index: 999;
    }
    
    .masked-img {
        overflow: hidden;
        position: relative;
    }

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js">
</script>

<input id="fileup" name="fileup" type="file" style="display:none">

<div id="container" class="container">
</div>

这里是Video link，代码是Pastebin和Fiddle和Codepen

Answer 1

我对整体实现感到困惑，并且有多行以无分号结尾。无论如何，根本原因是在container.selected()内部。您无需实施查找所选画布的方法。通过使用div.find("canvas").on('touchend mouseup', function(event) {...};附加事件，浏览器将为您触发具有正确目标的事件。触发事件时，将调用侦听器。目标是在事件对象（即event.currentTarget）中给出的。这就是事件监听器的精神。

原始container.selected()通过使用鼠标指针位置来预测要触摸哪个画布。由于框形图像和蒙版图像具有一定的重叠区域，因此结果可能包含两个画布，并且将z-index应用于错误的画布。

我将container.selected()修改如下

container.selected = function(ev) {
    var pos = container.mousePosition(ev);
    var item = ev.currentTarget;

    JQmasks.forEach(function(el) {
        var id = $(item).attr("id");
        if (el.id == id)
            el.item.enable();
        else
            el.item.disable();
    });
};

分配较高的z索引以遮盖图像

1 个答案: