Lumia Imaging SDK image blending creates separation lines

Question

I\'m trying to create a tiled background using the Lumia Imaging SDK\'s JpegTools.BlendAsync() method. I call the method in a loop to merge all the tiled images. Th

Answer 1

As discussed in the comments, I suggest an alternate way of doing this: By using a more "standard" rendering chain, instead of using JpegTools.

Some of this is based on your code sample, but I've tried making it as general as possible.

int outBgWidth = (int)bgSize.Width;
int outBgHeight = (int)bgSize.Height;
int tileWidth = (int)tileSize.Width;
int tileHeight = (int)tileSize.Height;

int currentBgWidth = 0;
int currentBgHeight = 0;

Point blendPosition = new Point(0, 0);

using (var backgroundCanvas = new ColorImageSource(new Size(outBgWidth, outBgHeight), Color.FromArgb(255, 0, 0, 0)))  //Create a black canvas with the output size.
using (var tileSource = new BitmapImageSource(bitmapSource))
using (var renderer = new JpegRenderer(backgroundCanvas))
{
    while (currentBgHeight < outBgHeight)
    {
        while (currentBgWidth < outBgWidth)
        {
            var blendEffect = new BlendEffect();
            blendEffect.BlendFunction = BlendFunction.Normal;
            blendEffect.GlobalAlpha = 1.0;

            blendEffect.Source = renderer.Source;
            blendEffect.ForegroundSource = tileSource;
            blendEffect.TargetArea = new Rect(blendPosition, new Size(0, 0));   //Since we are PreservingSize the size doesn't matter. Otherwise it must be in relative coordinate space!
            blendEffect.TargetOutputOption = OutputOption.PreserveSize;

            renderer.Source = blendEffect;

            currentBgWidth += tileWidth;
            blendPosition.X = (double)currentBgWidth / (double)outBgWidth;  //Careful, the target area is in relative coordinates
        }

        currentBgHeight += tileHeight;
        blendPosition.Y = (double)currentBgHeight / (double)outBgHeight;    //Careful, the target area is in relative coordinates
        blendPosition.X = 0.0;
        currentBgWidth = 0;
    }

    var result = await renderer.RenderAsync();   //An IBuffer containing the Jpeg file
}

I have tried this solution in a sample and I can't see any artifacts. Please do come back and report your results though!