Question

我使用以下函数在MKMapView的UIImage快照上绘制折线。该功能有效，但对我的目的来说太慢了。反正是为了加快速度吗？

func drawLineOnImageFromLocations(image: UIImage, snapshot: MKMapSnapshot,
                                  polylineLocations: [CLLocation], color: CGColor) -> UIImage {

    UIGraphicsBeginImageContextWithOptions(image.size, true, 0)

    // draw original image into the context
    image.draw(at: CGPoint.zero)

    // get the context for CoreGraphics
    guard let context = UIGraphicsGetCurrentContext() else {
        return image
    }

    context.beginPath()
    context.setLineWidth(10)
    context.setStrokeColor(color)
    let coordinates = polylineLocations.map{$0.coordinate}
    var points = [CGPoint]()
    for coordinate in coordinates {
        let point = snapshot.point(for: coordinate)
        points.append(point)
    }
    context.addLines(between: points)
    context.strokePath()

    // get the image from the graphics context
    let resultImage = UIGraphicsGetImageFromCurrentImageContext()
    // end the graphics context
    UIGraphicsEndImageContext()

    return resultImage!
}

Answer 1

结果是呼唤：

var count = 0;
.......
JSZipUtils.getBinaryContent(imageUrl, function (err, data) {
            if (err) {
                // throw err; // or handle the error
                console.log(err);
            }
            else {
                zip.file(fileName, data, { binary: true });
                count++;                    
                if (count == selectedImages.length) {                        
                    zip.generateAsync({ type: "blob" }).then(function (base64) {                            
                    //    window.location.replace("data:application/zip;base64," + base64);

                        saveAs(base64, `archive.zip`);

                        console.log("inner");
                    });
                }
            }
        });

是一项非常昂贵的操作。如果你能重构你的代码只是一次调用它会大大加快速度。

如何更快地在MKMapSnapshot上绘图？

1 个答案: