skiasharp xamarin forms: antialias on scaled bitmap poor - xamarin.forms

I'm drawing a bitmap with SkiaSharp in Xamarin Forms. The antialiasing is poor and I would like to know how I can improve it.
The source bitmap has antialiasing, shown in the left of the attached image. The right half shows a part of a screen capture on an Android device.
On the left part, notice that the aliasing is regular - a bit of dark feathering going upward and a bit of light feathering going downward, all uniform. On the right part we still see both feathering but it alternates between double wide pixels and single wide pixels.
When drawing the bitmap
canvas.DrawBitmap(bmpSrc, rectSrcRight, rectDest, paint);
I've tried setting the paint IsAntialiasing() true and false. No significant difference.
In this example, the source image is 61 pixels tall and the Android image is 102.
Am I expecting too much ?

You could have a try with the following code:
SKPaint paint = new SKPaint
{
IsAntialias = true,
FilterQuality = SKFilterQuality.High
};
canvas.DrawBitmap(bmpSrc, rectSrcRight, rectDest, paint);
Although IsAntialias will not work for bitmap, I also add it. If you want to draw bitmap continually, it will use more memory.
If you have a better way to make it work and not using more memory, please share here to discuss.

Related

constructing a bitmap from stream rotates the image

I am using ASP.Net with VB and doing some file uploads. Sometimes, when a bitmap is constructed from the file input stream, the image gets rotated. It doesn't seem to happen if the image is wider than it is tall, but also doesn't seem to happen all the time if the image is taller than wide. I have provided a few screen shots where the properties of the image are show, and the created bitmap's properties are shown at run time.
Any ideas what is happening here or what we can do to prevent this rotation?
Rotated image:
Non-rotated image:
Using the rotation code found Here fixed it. The images were coming from a phone camera and had original orientation information stored in them that could be used to right them.

QPainter drawImage becomes very pixelated

I use QPainter and the function drawImage to draw an airplane on a map. The image and redrawn each time the position of the airplane changes. The problem is, after some time, the image becomes extremely pixelated. I have tried to use a high quality .svg and that did not help either.
Below is my code. Can somebody spot where the error is or what has caused the image to be so pixelated?
// Load .svg image
airplane->load("AirplaneTopDown.svg");
// Downsize image
airplaneSmall = airplane->scaled(120, 120,Qt::KeepAspectRatio);
// Rotate image by trans
airplaneSmall = airplaneSmall.transformed(trans);
// Draw image and center at a certain screen position
painter.drawImage(airplaneX-airplaneSmall.width()/2,airplaneY-airplaneSmall.height()/2,airplaneSmall);
Below are the images of the drawn airplanes. One taken as screenshot at the beginning of the program runtime another one taken after a couple of minutes.
Airplane
Airplane-pixelated
One of your problems is that you first rescale the image and then rotate it.
The rotation needs to interpolate new pixels from the old ones. The higher the resolution of the input, the better the quality of the interpolation. The quality of your SVG is completely lost after the rescale operation.
The second problem you are facing is that you use the "fast" (default) transformation method. This method does not antialias. So instead of interpolating from several input pixels, it will only take one best fit. Calling transformed() with the second argument Qt::SmoothTransformation and scaled() with the sceond argument Qt::SmoothTransformation |Qt::KeepAspectRatio` will greatly improve your results.
However it is also slower, as is performing the rotation on the image in its original, higher resolution.
The arguably best solution to your problem is to take on a different approach. Instead of loading the SVG into a QImage, which is a raster-based image, you should work with the vector graphics. So the SVG is rendered in the right orientation and scale in the first place. A good starting point is the SVG Viewer Example: http://doc.qt.io/qt-5/qtsvg-svgviewer-example.html

Unity3D: Strange 1 pix white line between tiles on my 2D game

My game have a tiled 2d map. This is a scene screenshot:
I found when I move the camera vertically, there are strange white lines randomly appeared between randomly tiles, See:
I don't know why....
PS: This is a pixel style 2d game, so my texture's filter mode is "Point".
PS: I uploaded this test scene at https://dl.dropbox.com/u/53858613/Web/Web.html , Hold the left mouse button , camera will move downwards, then you'll see white lines randomly.
Change your materials shader to something more suited for 2D. Such as sprite/default.
I made a quick test project and changing the shader from "diffuse" to "sprite/default" solved the issue.
What fixed it for me is setting the compression for my 2D spritesheet to point instead of bi-linear
I do not see this issue on my machine with your example project.
It seems just fine.
1) Make sure there is no white line in the actual image.
2) Make sure resolution options are not an issue.
3) I am not 100% sure but in the skybox the same happens with BLACK lines. Try and change the texture's texture mode to Clamp if possible. This might resolve the issue.
Hope this helps,
-Smileynator
According to this Tilemap tutorial by Brackeys, try turning off antialiasing under Edit>Project Settings>Quality>Anti Aliasing.

QImage loads with wrong orientation for certain images

I am instantiating a QImage from an image file like below and subsequently rendering it on a QWidget.
QImage ( const QString & fileName, const char * format = 0 )
For most images, everything works fine. But for a few images, the QImage gets loaded with a 90-degree rotated image.
It seems this happens only with pictures taken earlier on my phone in portrait mode. Those taken in landscape are fine
You might need to use a library like libexif to determine the photo orientation and then rotate the QImage accordingly
Since Qt 5.5 set Image.autoTransform : true because the default is false!
QT Image QML Type reference
With C++ Qt-class QImageReader:
QImageReader imgReader( imagePath );
imgReader.setAutoTransform( true );
QImage img = imgReader.read();
https://discussions.apple.com/thread/2541504?start=0&tstart=0
It sounds like it is a pretty common issue, where there is some flag or tag added on the image that says how to rotate it, instead of actually reordering the pixels in the image. For the image you are trying to render, you could go and take the format you are trying to use, and see if there are any extra flags you could check and have Qt do the rotation.
Sounds like cppguy knows of a library that can let you check these flags.
EDIT Found a better description for it:
johninsj - Re: iPhone 4 Photo's & Video Rotating Sideways In Email
Nov 2, 2010 1:45 PM (in response to VibrantRedGT)
Apple sets the jpeg meta tag for orientation when you shoot a photo,
so if you hold the iphone upside down, or sideways, etc, the image
(which is shot upside down or sideways, since the camera is upside
down/sideways) knows it needs to flip/rotate the image when you look
at it.
Not all software honors the rotation settings. Gimp (which runs on
everything, and is free) does.
You can rotate images and save them, or learn to shoot photos with the
iPhone in the correct orientation for non-rotated images. That would
be with the home button to the right as you look at the screen.
Hope that helps.

Advanced Image cropping and image resizing in Flex

I have created a image cropping tool in flex using core copyPixel method.
croppedBitmapData.copyPixels(croppedBitmapData, clipCan, new Point(0, 0));
I have to crope area of dementions 20*20 and show this cropped area in an image of demention 250*350.
Every thing going well.
My problem is image distortion.
Even i am using this method for smoothing image contents on complete.
private function smoothImage(event:Event):void
{
var bitmap: Bitmap = ((event.target as Image).content as Bitmap);
if (bitmap != null)
{
bitmap.smoothing = true;
}
}
I want to get the result of this site. http://www.yourplayingcards.com/builder/
Please help me to get ride of image distortion.
Can we show bitmapdata of 20*20 into image of 250*350 without distotion?
What you call 'distortion' is probably what I think you mean by pixelation. The reason why that website can zoom in without pixelation is because it's using vector shapes, not bitmaps, to show the graphics. Vector shapes can be scale infinitely without loss of quality because it doesn't store pixel information, but spline information.
In essence, if you want to imitate the zooming of the the website you have shown, you will have to create your own vector shape. You can use Flex 4's built in FXG format or use something like Degrafa if you're still in Flex 3. You can also leverage Flash Catalyst to import vector graphics made in Illustration into Flex.
I am not sure about that but it is done in VectorMagic may be they are using server side too any ways, you may also interested in Actionscript SVG renderer
Hopes that helps

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