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C# Winform OnPaint flickering

I am recreating a simple tile based game (ref: Javidx9 cpp tile game) on c# winforms and the screen flickers as i move, I have DoubleBuffered = true. i will show an example with textures and one without.
TEXTURES > e.Graphics.DrawImage()
NO TEXTURES > e.Graphics.FillRectangle()
in the code I made a GameManager, CameraManager, PlayerModel, lastly the form OnPaint that draws the game information. the way it works is the GameManager tells the Player to update itself depending on user input (move, jump, ect...), then tells the Camera to update depending on the players position. at first i called the GameManager.Update() from the Paint event but then i separated the Paint event from the GameManager and made the GameManager update asynchronous because the Paint event updates too slow. thats when the problem started.
//GameManager
public void CreateSoloGame(MapModel map)
{
CurrentMap = map;
ResetPlayer();
_inGame = true;
new Task(() =>
{
while (_inGame)
{
Elapsed = _stopwatch.ElapsedMilliseconds;
_stopwatch.Restart();
int i = 0;
Step(Elapsed);
while (i < _gameTime) //_gameTime controls the speed of the game
{
i++;
}
}
}).Start();
}
public void Step(double elapsed)
{
Player.Update(CurrentMap, elapsed);
Camera.SetCamera(Player.Position, CurrentMap);
}
//PlayerModel
public void DetectCollision(MapModel CurrentMap, double Elapsed)
{
//adds velocity to players position
float NextPlayerX = Position.X + (VelX * (float)Elapsed);
float NextPlayerY = Position.Y + (VelY * (float)Elapsed);
//collision detection
OnFloor = false;
if (VelY > 0)
{
//bottom
if (CurrentMap.GetTile((int)(Position.X + .1), (int)(NextPlayerY + 1)) == '#' || CurrentMap.GetTile((int)(Position.X + .9), (int)(NextPlayerY + 1)) == '#')
{
NextPlayerY = (int)NextPlayerY;
VelY = 0;
OnFloor = true;
_jumps = 2;
}
}
else
{
//top
if (CurrentMap.GetTile((int)(Position.X + .1), (int)NextPlayerY) == '#' || CurrentMap.GetTile((int)(Position.X + .9), (int)NextPlayerY) == '#')
{
NextPlayerY = (int)NextPlayerY + 1;
VelY = 0;
}
}
if (VelX < 0)
{
//left
if (CurrentMap.GetTile((int)NextPlayerX, (int)Position.Y) == '#' || CurrentMap.GetTile((int)NextPlayerX, (int)(Position.Y + .9)) == '#')
{
NextPlayerX = (int)NextPlayerX + 1;
VelX = 0;
}
}
else
{
//right
if (CurrentMap.GetTile((int)(NextPlayerX + 1), (int)Position.Y) == '#' || CurrentMap.GetTile((int)(NextPlayerX + 1), (int)(Position.Y + .9)) == '#')
{
NextPlayerX = (int)NextPlayerX;
VelX = 0;
}
}
//updates player position
Position = new PointF(NextPlayerX, NextPlayerY);
}
public void Jump()
{
if (_jumps > 0)
{
VelY = -.06f;
_jumps--;
}
}
public void ReadInput(double elapsed)
{
//resets velocity back to 0 if player isnt moving
if (Math.Abs(VelY) < 0.001f) VelY = 0;
if (Math.Abs(VelX) < 0.001f) VelX = 0;
//sets velocity according to player input - S and W are used for no clip free mode
//if (UserInput.KeyInput[Keys.W]) _playerVelY -= .001f;
//if (UserInput.KeyInput[Keys.S]) _playerVelY += .001f;
if (Input.KEYINPUT[Keys.A]) VelX -= .001f * (float)elapsed;
else if (Input.KEYINPUT[Keys.D]) VelX += .001f * (float)elapsed;
else if (Math.Abs(VelX) > 0.001f && OnFloor) VelX += -0.06f * VelX * (float)elapsed;
//resets jumping
if (!OnFloor)
VelY += .0004f * (float)elapsed;
//limits velocity
//if (_playerVelY <= -.014) _playerVelY = -.014f; //disabled to allow jumps
if (VelY >= .05) VelY = .05f;
if (VelX >= .02 && !Input.KEYINPUT[Keys.ShiftKey]) VelX = .02f;
else if (VelX >= .005 && Input.KEYINPUT[Keys.ShiftKey]) VelX = .005f;
if (VelX <= -.02 && !Input.KEYINPUT[Keys.ShiftKey]) VelX = -.02f;
else if (VelX <= -.005 && Input.KEYINPUT[Keys.ShiftKey]) VelX = -.005f;
}
public void Update(MapModel map, double elapsed)
{
ReadInput(elapsed);
DetectCollision(map, elapsed);
}
//CameraManager
public void SetCamera(PointF center, MapModel map, bool clamp = true)
{
//changes the tile size according to the screen size
TileSize = Input.ClientScreen.Width / Tiles;
//amount of tiles along thier axis
TilesX = Input.ClientScreen.Width / TileSize;
TilesY = Input.ClientScreen.Height / TileSize;
//camera offset
OffsetX = center.X - TilesX / 2.0f;
OffsetY = center.Y - TilesY / 2.0f;
//make sure the offset does not go beyond bounds
if (OffsetX < 0 && clamp) OffsetX = 0;
if (OffsetY < 0 && clamp) OffsetY = 0;
if (OffsetX > map.MapWidth - TilesX && clamp) OffsetX = map.MapWidth - TilesX;
if (OffsetY > map.MapHeight - TilesY && clamp) OffsetY = map.MapHeight - TilesY;
//smooths out movement for tiles
TileOffsetX = (OffsetX - (int)OffsetX) * TileSize;
TileOffsetY = (OffsetY - (int)OffsetY) * TileSize;
}
//Form Paint event
private void Draw(object sender, PaintEventArgs e)
{
Brush b;
Input.ClientScreen = ClientRectangle;
for (int x = -1; x < _camera.TilesX + 1; x++)
{
for (int y = -1; y < _camera.TilesY + 1; y++)
{
switch (_map.GetTile(x + (int)_camera.OffsetX, y + (int)_camera.OffsetY))
{
case '.':
//e.Graphics.DrawImage(sky, x * _camera.TileSize - _camera.TileOffsetX, y * _camera.TileSize - _camera.TileOffsetY, _camera.TileSize, _camera.TileSize);
//continue;
b = Brushes.MediumSlateBlue;
break;
case '#':
//e.Graphics.DrawImage(block, x * _camera.TileSize - _camera.TileOffsetX, y * _camera.TileSize - _camera.TileOffsetY, _camera.TileSize, _camera.TileSize);
//continue;
b = Brushes.DarkGray;
break;
case 'o':
b = Brushes.Yellow;
break;
case '%':
b = Brushes.Green;
break;
default:
b = Brushes.MediumSlateBlue;
break;
}
e.Graphics.FillRectangle(b, x * _camera.TileSize - _camera.TileOffsetX, y * _camera.TileSize - _camera.TileOffsetY, (x + 1) * _camera.TileSize, (y + 1) * _camera.TileSize);
}
}
e.Graphics.FillRectangle(Brushes.Purple, (_manager.Player.Position.X - _camera.OffsetX) * _camera.TileSize, (_manager.Player.Position.Y - _camera.OffsetY) * _camera.TileSize, _camera.TileSize, _camera.TileSize);
//e.Graphics.DrawImage(chef, (_manager.Player.Position.X - _camera.OffsetX) * _camera.TileSize, (_manager.Player.Position.Y - _camera.OffsetY) * _camera.TileSize, _camera.TileSize, _camera.TileSize);
Invalidate();
}
P.S. i use winforms because i dont work with GUIs much and its the one im most familiar with and this is just something quick i wanted to try out but i've never had this issue. i tried a couple of things but nothing worked so this is my last resort. if you think i should use another GUI let me know and ill look into it. also if you think my code is ugly lmk why.

Fill the form with a PictureBox and hook into the .Paint() event. For some reason, there is no flicker drawing on a PictureBox compared to drawing on a form.
Also having a game loop improves things a lot. I am getting 600+ fps with my example code.
full code below:
public partial class RunningForm1 : Form
{
static readonly Random rng = new Random();
float offset;
int index;
Queue<int> town;
const int grid = 12;
Color[] pallete;
FpsCounter clock;
#region Windows API - User32.dll
[StructLayout(LayoutKind.Sequential)]
public struct WinMessage
{
public IntPtr hWnd;
public Message msg;
public IntPtr wParam;
public IntPtr lParam;
public uint time;
public System.Drawing.Point p;
}
[System.Security.SuppressUnmanagedCodeSecurity] // We won't use this maliciously
[DllImport("User32.dll", CharSet = CharSet.Auto)]
public static extern bool PeekMessage(out WinMessage msg, IntPtr hWnd, uint messageFilterMin, uint messageFilterMax, uint flags);
#endregion
public RunningForm1()
{
InitializeComponent();
this.pic.Paint += new PaintEventHandler(this.pic_Paint);
this.pic.SizeChanged += new EventHandler(this.pic_SizeChanged);
//Initialize the machine
this.clock = new FpsCounter();
}
protected override void OnLoad(EventArgs e)
{
base.OnLoad(e);
Setup();
System.Windows.Forms.Application.Idle += new EventHandler(OnApplicationIdle);
}
void UpdateMachine()
{
pic.Refresh();
}
#region Main Loop
private void OnApplicationIdle(object sender, EventArgs e)
{
while (AppStillIdle)
{
// Render a frame during idle time (no messages are waiting)
UpdateMachine();
}
}
private bool AppStillIdle
{
get
{
WinMessage msg;
return !PeekMessage(out msg, IntPtr.Zero, 0, 0, 0);
}
}
#endregion
private void pic_SizeChanged(object sender, EventArgs e)
{
pic.Refresh();
}
private void pic_Paint(object sender, PaintEventArgs e)
{
// Show FPS counter
var fps = clock.Measure();
var text = $"{fps:F2} fps";
var sz = e.Graphics.MeasureString(text, SystemFonts.DialogFont);
var pt = new PointF(pic.Width - 1 - sz.Width - 4, 4);
e.Graphics.DrawString(text, SystemFonts.DialogFont, Brushes.Black, pt);
// draw on e.Graphics
e.Graphics.SmoothingMode = SmoothingMode.HighQuality;
e.Graphics.TranslateTransform(0, pic.ClientSize.Height - 1);
e.Graphics.ScaleTransform(1, -1);
int wt = pic.ClientSize.Width / (grid - 1);
int ht = pic.ClientSize.Height / (grid + 1);
SolidBrush fill = new SolidBrush(Color.Black);
for (int i = 0; i < town.Count; i++)
{
float x = offset + i * wt;
var building = new RectangleF(
x, 0,
wt, ht * town.ElementAt(i));
fill.Color = pallete[(index + i) % pallete.Length];
e.Graphics.FillRectangle(fill, building);
}
offset -= 0.4f;
if (offset <= -grid - wt)
{
UpdateTown();
offset += wt;
}
}
private void Setup()
{
offset = 0;
index = 0;
town = new Queue<int>();
pallete = new Color[]
{
Color.FromKnownColor(KnownColor.Purple),
Color.FromKnownColor(KnownColor.Green),
Color.FromKnownColor(KnownColor.Yellow),
Color.FromKnownColor(KnownColor.SlateBlue),
Color.FromKnownColor(KnownColor.LightCoral),
Color.FromKnownColor(KnownColor.Red),
Color.FromKnownColor(KnownColor.Blue),
Color.FromKnownColor(KnownColor.LightCyan),
Color.FromKnownColor(KnownColor.Crimson),
Color.FromKnownColor(KnownColor.GreenYellow),
Color.FromKnownColor(KnownColor.Orange),
Color.FromKnownColor(KnownColor.LightGreen),
Color.FromKnownColor(KnownColor.Gold),
};
for (int i = 0; i <= grid; i++)
{
town.Enqueue(rng.Next(grid) + 1);
}
}
private void UpdateTown()
{
town.Dequeue();
town.Enqueue(rng.Next(grid) + 1);
index = (index + 1) % pallete.Length;
}
}
public class FpsCounter
{
public FpsCounter()
{
this.PrevFrame = 0;
this.Frames = 0;
this.PollOverFrames = 100;
this.Clock = Stopwatch.StartNew();
}
/// <summary>
/// Use this method to poll the FPS counter
/// </summary>
/// <returns>The last measured FPS</returns>
public float Measure()
{
Frames++;
PrevFrame++;
var dt = Clock.Elapsed.TotalSeconds;
if (PrevFrame > PollOverFrames || dt > PollOverFrames / 50)
{
LastFps = (float)(PrevFrame / dt);
PrevFrame = 0;
Clock.Restart();
}
return LastFps;
}
public float LastFps { get; private set; }
public long Frames { get; private set; }
private Stopwatch Clock { get; }
private int PrevFrame { get; set; }
/// <summary>
/// The number of frames to average to get a more accurate frame count.
/// The higher this is the more stable the result, but it will update
/// slower. The lower this is, the more chaotic the result of <see cref="Measure()"/>
/// but it will get a new result sooner. Default is 100 frames.
/// </summary>
public int PollOverFrames { get; set; }
}

How to resize custom markers depending on zoom level in GMap.NET?

I'm creating GMap.NET app and added some custom markers on it. Is it possible to make them scale depending on the zoom level of the map?

You will need to create a custom GMapMarker and use the zoom level in the OnRender() to scale the image. Each zoom level has a different ratio but luckily for you, I have mesured them all. Not sure if the ratio changes with different map providers?
You can set the x/y scale and heading using a seperate thread and it will update in real time.
The "defaultZoomLevel" will set the zoom level at which the image has a 1:1 ratio. I have only tried the value 16, not sure it will work for other values you may need to calculate all the ratios for each value or extract the curve from the data and use that to scale the ratio.
Use this to set the zoom level when it changes:
private void Gmap_OnMapZoomChanged()
{
//trackBar_Zoom.Value = (int)Gmap.Zoom;
//label_Zoom.Text = "Zoom: " + trackBar_Zoom.Value.ToString();
SelectedOverlay?.SetZoomLevel(Gmap.Zoom);
}
Use it like:
SelectedOverlay = new GMapMarkerImageOverlay(Gmap.Position, 0, 1, 1, Gmap.Zoom, Resources.GreySquare);
Overlay_ImageOverlays.Markers.Add(SelectedOverlay);
And this is the MapMarker:
public class GMapMarkerImageOverlay : GMapMarker
{
private readonly double deg2rad = 3.14159265 / 180.0;
private readonly double rad2deg = 180 / 3.14159265;
private readonly float defaultZoomLevel = 16;
private float zoomRatio = 1f;
private float heading = 0;
private double zoom = 0;
private float scaleX = 0;
private float scaleY = 0;
private Bitmap overlayImage;
private void SetZoomRatio()
{
if (zoom < 12)
{
zoomRatio = 0.045f;
}
else if (zoom == 12)
{
zoomRatio = 0.08f;
}
else if (zoom == 13)
{
zoomRatio = 0.155f;
}
else if (zoom == 14)
{
zoomRatio = 0.285f;
}
else if (zoom == 15)
{
zoomRatio = 0.53f;
}
else if (zoom == 16)
{
zoomRatio = 1f;
}
else if (zoom == 17)
{
zoomRatio = 1.88f;
}
else if (zoom == 18)
{
zoomRatio = 3.55f;
}
else if (zoom == 19)
{
zoomRatio = 6.75f;
}
else if (zoom == 20)
{
zoomRatio = 11.5f;
}
else
{
zoomRatio = 11.5f;
}
}
public GMapMarkerImageOverlay(PointLatLng p, float heading, float scaleX, float scaleY, double zoom, Bitmap image)
: base(p)
{
overlayImage = image;
this.heading = heading;
this.scaleX = scaleX;
this.scaleY = scaleY;
this.zoom = zoom;
SetZoomRatio();
}
internal void SetPosition(PointLatLng position)
{
//Position = position;
//LocalPosition = position;
}
public void SetHeading(float h)
{
heading = h;
}
public void SetZoomLevel(double z)
{
zoom = z;
SetZoomRatio();
//Util.Log($"Zoom level: {z}");
}
public void SetScaleX(float x)
{
scaleX = x;
}
public void SetScaleY(float y)
{
scaleY = y;
}
public void SetRatio(float r)
{
zoomRatio = r;
}
public override void OnRender(Graphics g)
{
try
{
var temp = g.Transform;
g.TranslateTransform(LocalPosition.X, LocalPosition.Y);
float ratio = (float)zoom / defaultZoomLevel;
ratio *= zoomRatio;
g.ScaleTransform(scaleX*ratio, scaleY*ratio);
base.ToolTipMode = MarkerTooltipMode.OnMouseOver;
base.ToolTipText = $"Ratio:{ratio}";
// anti NaN
try
{
g.RotateTransform(heading);
}
catch
{
}
var sIcon = overlayImage;
sIcon = new Bitmap(sIcon, sIcon.Width / 1, sIcon.Height / 1);
g.DrawImageUnscaled(sIcon, sIcon.Width / -2, sIcon.Height / -2);
g.Transform = temp;
}
catch (Exception ex)
{
//Util.Log(ex);
}
}
}

Zoom and translate an Image from the mouse location

Issue: Attempting to zoom (scale) an Image from (or at the) mouse location using transforms in the Paint event to translate bitmap origin to mouse location, then scale the Image and translate its origin back.
The Image jumps and fails to scale from the relocated origin when translating the mouse location.
Rotate, scale, and pan function correctly without translating to the the mouse location.
Running on .Net 4.7.2, using Visual Studio in Windows 10 1909
v18363.778
The relevant code blocks:
private void trackBar1_Scroll(object sender, EventArgs e)
{
// Get rotation angle
ang = trackBar1.Value;
pnl1.Invalidate();
}
private void pnl1_MouseWheel(object sender, MouseEventArgs e)
{
// Get mouse location
mouse = e.location;
// Get new scale (zoom) factor
zoom = (float)(e.Delta > 0 ? zoom * 1.05 : zoom / 1.05);
pnl1.Invalidate();
}
private void pnl1_MouseDown(object sender, MouseEventArgs e)
{
if (e.Button != MouseButtons.Left) return;
pan = true;
mouX = e.X;
mouY = e.Y;
oldX = imgX;
oldY = imgY;
}
private void pnl1_MouseMove(object sender, MouseEventArgs e)
{
if (e.Button != MouseButtons.Left || !pan) return;
// Coordinates of panned image
imgX = oldX + e.X - mouX;
imgY = oldY + e.Y - mouY;
pnl1.Invalidate();
}
private void pnl1_MouseUp(object sender, MouseEventArgs e)
{
pan = false;
}
private void pnl1_Paint(object sender, PaintEventArgs e)
{
// Apply rotation angle # center of bitmap
e.Graphics.TranslateTransform(img.Width / 2, img.Height / 2);
e.Graphics.RotateTransform(ang);
e.Graphics.TranslateTransform(-img.Width / 2, -img.Height / 2);
// Apply scaling factor - focused # mouse location
e.Graphics.TranslateTransform(mouse.X, mouse.Y, MatrixOrder.Append);
e.Graphics.ScaleTransform(zoom, zoom, MatrixOrder.Append);
e.Graphics.TranslateTransform(-mouse.X, -mouse.Y, MatrixOrder.Append);
// Apply drag (pan) location
e.Graphics.TranslateTransform(imgX, imgY, MatrixOrder.Append);
// Draw "bmp" # location
e.Graphics.DrawImage(img, 0, 0);
}

A few suggestions and a couple of tricks.
Not exactly tricks, just some methods to speed up the calculations when more than one graphic transformation is in place.
Divide and conquer: split the different graphics effects and transformations in different, specialized, methods that do one thing. Then design in a way that makes it possible for these methods to work together when needed.
Keep it simple: when Graphics objects need to accumulate more than a couple of transformations, the order in which Matrices are stacked can cause misunderstandings. It's simpler (and less prone to generate weird outcomes) to calculate some generic transformations (translate and scale, mostly) beforehand, then let GDI+ render already pre-cooked objects and shapes.
Here, only Matrix.RotateAt and Matrix.Multiply are used.
Some notes about Matrix transformations here: Flip the GraphicsPath
Use the right tools: for example, a Panel used as canvas is not exactly the best choice. This Control is not double-buffered; this feature can be enabled, but the Panel class is not meant for drawing, while a PictureBox (or a non-System flat Label) supports it on its own.
Some more notes here: How to apply a fade transition effect to Images
The sample code shows 4 zoom methods, plus generates rotation transformations (which work side-by-side, don't accumulate).
The Zoom modes are selected using an enumerator (private enum ZoomMode):
Zoom modes:
ImageLocation: Image scaling is performed in-place, keeping the current Location on the canvas in a fixed position.
CenterCanvas: while the Image is scaled, it remains centered on the Canvas.
CenterMouse: the Image is scaled and translated to center itself on the current Mouse location on the Canvas.
MouseOffset: the Image is scaled and translated to maintain a relative position determined by the initial location of the Mouse pointer on the Image itself.
You can notice that the code simplifies all the calculations, applying translations exclusively relative to the Rectangle that defines the current Image bounds and only in relation to the Location of this shape.
The Rectangle is only scaled when the calculation needs to preemptively determine what the Image size will be after the Mouse Wheel has generated the next Zoom factor.
Visual sample of the implemented functionalities:
Sample code:
canvas is the Custom Control, derived from PictureBox (you can find its definition at the bottom). This control is added to the Form in code, here. Modify as needed.
trkRotationAngle is the TrackBar used to define the current rotation of the Image. Add this control to the Form in the designer.
radZoom_CheckedChanged is the event handler of all the RadioButtons used to set the current Zoom Mode. The value these Controls set is assigned in their Tag property. Add these controls to the Form in the designer.
using System.Drawing;
using System.Drawing.Drawing2D;
using System.IO;
using System.Windows.Forms;
public partial class frmZoomPaint : Form
{
private float rotationAngle = 0.0f;
private float zoomFactor = 1.0f;
private float zoomStep = .05f;
private RectangleF imageRect = RectangleF.Empty;
private PointF imageLocation = PointF.Empty;
private PointF mouseLocation = PointF.Empty;
private Bitmap drawingImage = null;
private PictureBoxEx canvas = null;
private ZoomMode zoomMode = ZoomMode.ImageLocation;
private enum ZoomMode
{
ImageLocation,
CenterCanvas,
CenterMouse,
MouseOffset
}
public frmZoomPaint()
{
InitializeComponent();
string imagePath = [Path of the Image];
drawingImage = (Bitmap)Image.FromStream(new MemoryStream(File.ReadAllBytes(imagePath)));
imageRect = new RectangleF(Point.Empty, drawingImage.Size);
canvas = new PictureBoxEx(new Size(555, 300));
canvas.Location = new Point(10, 10);
canvas.MouseWheel += canvas_MouseWheel;
canvas.MouseMove += canvas_MouseMove;
canvas.MouseDown += canvas_MouseDown;
canvas.MouseUp += canvas_MouseUp;
canvas.Paint += canvas_Paint;
Controls.Add(canvas);
}
private void canvas_MouseWheel(object sender, MouseEventArgs e)
{
mouseLocation = e.Location;
float zoomCurrent = zoomFactor;
zoomFactor += e.Delta > 0 ? zoomStep : -zoomStep;
if (zoomFactor < .10f) zoomStep = .01f;
if (zoomFactor >= .10f) zoomStep = .05f;
if (zoomFactor < .0f) zoomFactor = zoomStep;
switch (zoomMode) {
case ZoomMode.CenterCanvas:
imageRect = CenterScaledRectangleOnCanvas(imageRect, canvas.ClientRectangle);
break;
case ZoomMode.CenterMouse:
imageRect = CenterScaledRectangleOnMousePosition(imageRect, e.Location);
break;
case ZoomMode.MouseOffset:
imageRect = OffsetScaledRectangleOnMousePosition(imageRect, zoomCurrent, e.Location);
break;
default:
break;
}
canvas.Invalidate();
}
private void canvas_MouseDown(object sender, MouseEventArgs e)
{
if (e.Button != MouseButtons.Left) return;
mouseLocation = e.Location;
imageLocation = imageRect.Location;
canvas.Cursor = Cursors.NoMove2D;
}
private void canvas_MouseMove(object sender, MouseEventArgs e)
{
if (e.Button != MouseButtons.Left) return;
imageRect.Location =
new PointF(imageLocation.X + (e.Location.X - mouseLocation.X),
imageLocation.Y + (e.Location.Y - mouseLocation.Y));
canvas.Invalidate();
}
private void canvas_MouseUp(object sender, MouseEventArgs e) =>
canvas.Cursor = Cursors.Default;
private void canvas_Paint(object sender, PaintEventArgs e)
{
var drawingRect = GetDrawingImageRect(imageRect);
using (var mxRotation = new Matrix())
using (var mxTransform = new Matrix()) {
e.Graphics.InterpolationMode = InterpolationMode.HighQualityBicubic;
e.Graphics.PixelOffsetMode = PixelOffsetMode.Half;
mxRotation.RotateAt(rotationAngle, GetDrawingImageCenterPoint(drawingRect));
mxTransform.Multiply(mxRotation);
e.Graphics.Transform = mxTransform;
e.Graphics.DrawImage(drawingImage, drawingRect);
}
}
private void trkRotationAngle_ValueChanged(object sender, EventArgs e)
{
rotationAngle = trkAngle.Value;
canvas.Invalidate();
canvas.Focus();
}
private void radZoom_CheckedChanged(object sender, EventArgs e)
{
var rad = sender as RadioButton;
if (rad.Checked) {
zoomMode = (ZoomMode)int.Parse(rad.Tag.ToString());
}
canvas.Focus();
}
#region Drawing Methods
public RectangleF GetScaledRect(RectangleF rect, float scaleFactor) =>
new RectangleF(rect.Location,
new SizeF(rect.Width * scaleFactor, rect.Height * scaleFactor));
public RectangleF GetDrawingImageRect(RectangleF rect) =>
GetScaledRect(rect, zoomFactor);
public PointF GetDrawingImageCenterPoint(RectangleF rect) =>
new PointF(rect.X + rect.Width / 2, rect.Y + rect.Height / 2);
public RectangleF CenterScaledRectangleOnCanvas(RectangleF rect, RectangleF canvas)
{
var scaled = GetScaledRect(rect, zoomFactor);
rect.Location = new PointF((canvas.Width - scaled.Width) / 2,
(canvas.Height - scaled.Height) / 2);
return rect;
}
public RectangleF CenterScaledRectangleOnMousePosition(RectangleF rect, PointF mousePosition)
{
var scaled = GetScaledRect(rect, zoomFactor);
rect.Location = new PointF(mousePosition.X - (scaled.Width / 2),
mousePosition.Y - (scaled.Height / 2));
return rect;
}
public RectangleF OffsetScaledRectangleOnMousePosition(RectangleF rect, float currentZoom, PointF mousePosition)
{
var currentRect = GetScaledRect(imageRect, currentZoom);
if (!currentRect.Contains(mousePosition)) return rect;
float scaleRatio = currentRect.Width / GetScaledRect(rect, zoomFactor).Width;
PointF mouseOffset = new PointF(mousePosition.X - rect.X, mousePosition.Y - rect.Y);
PointF scaledOffset = new PointF(mouseOffset.X / scaleRatio, mouseOffset.Y / scaleRatio);
PointF position = new PointF(rect.X - (scaledOffset.X - mouseOffset.X),
rect.Y - (scaledOffset.Y - mouseOffset.Y));
rect.Location = position;
return rect;
}
#endregion
}
The simple PictureBoxEx custom control (modify and extend as needed):
This PictureBox is selectable, so it can be focused, with a Mouse click
using System.ComponentModel;
using System.Drawing;
using System.Windows.Forms;
[DesignerCategory("Code")]
public class PictureBoxEx : PictureBox
{
public PictureBoxEx() : this (new Size(200, 200)){ }
public PictureBoxEx(Size size) {
SetStyle(ControlStyles.Selectable | ControlStyles.UserMouse, true);
BorderStyle = BorderStyle.FixedSingle;
Size = size;
}
}

#Jimi: Thank you for the detailed information - very useful for visualizing the concepts involved in the graphics manipulations. I had arrived at a functioning solution (see code below) however, your code utilizes steps with greater efficiency. Admittedly, my code is developed with more of an intent to learn the mechanics of image manipulation - as I am still at the early part of the learning curve. Nonetheless, your illustration of the mechanics and techniques is extremely helpful.
using System;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Windows.Forms;
namespace ZoomImage
{
public partial class Form1 : Form
{
Image img;
Bitmap bmp;
float ang = 0;
float zoom = 1;
bool pan;
bool? ctr = false;
Point mcurrent;
PointF mouse;
PointF image;
PointF _image;
PointF rotate;
public Form1()
{
InitializeComponent();
MouseWheel += mouseWheel;
img = Image.FromFile(#"C:\testimage.jpg");
bmp = new Bitmap(img);
// Set initial scale to fit canvas window
float wRatio = (float)pbx.Width / (float)img.Width;
float hRatio = (float)pbx.Height / (float)img.Height;
zoom = Math.Min(wRatio, hRatio);
image.X = (pbx.Width - zoom * img.Width) / 2;
image.Y = (pbx.Height - zoom * img.Height) / 2;
}
private void label()
{
string _imgX = string.Format("{0:000}", image.X);
string _imgY = string.Format("{0:000}", image.Y);
lbl1.Text = "Location: " + _imgX + ", " + _imgY + "\r\nRotation: " + ang + "\r\nZoom: " + zoom + "\r\nMouse: " + mcurrent.X + ", " + mcurrent.Y;
}
private void btnRotate_Click(object sender, EventArgs e)
{
if (ModifierKeys == Keys.Control)
{
string msg = "Set center of rotation point:\r\n\nMove mouse to desired center ";
msg += "of rotation then hold \"Alt\" and left-click.\r\n\n";
msg += "To restore center of rotation to center of image:\r\n\nHold \"Shift\" and";
msg += " click \"Rotate\".";
MessageBox.Show(msg,"Change center of rotation");
ctr = null;
pbx.Focus();
return;
}
else if (ModifierKeys == Keys.Shift)
{
ctr = false;
return;
}
ang = ang == 270 ? 0 : ang += 90;
if (ang > 360) ang -= 360;
trackBar1.Value = (int)ang;
ctr = ctr == null ? false : ctr;
if (ctr == false) rotate = new PointF(img.Width / 2, img.Height / 2);
pbx.Invalidate();
}
private void trackBar1_Scroll(object sender, EventArgs e)
{
ang = trackBar1.Value;
if (ctr == false) rotate = new PointF(img.Width / 2, img.Height / 2);
pbx.Invalidate();
}
private void mouseWheel(object sender, MouseEventArgs e)
{
mouse = new PointF(e.X - image.X, e.Y - image.Y);
float zinc = 0.05f;
float zfac = 1 + zinc;
zoom = (float)(e.Delta > 0 ? zoom * (zfac) : zoom / (zfac));
// Adjust "img" (bitmap) orgin to maintain fixed focus # mouse location
if (e.Delta > 0)
{
image.X -= zinc * mouse.X;
image.Y -= zinc * mouse.Y;
}
else
{
image.X += (1 - 1 / (zfac)) * mouse.X;
image.Y += (1 - 1 / (zfac)) * mouse.Y;
}
image = new PointF(image.X, image.Y);
pbx.Invalidate();
}
private void mouseDown(object sender, MouseEventArgs e)
{
if (e.Button != MouseButtons.Left) return;
if (ModifierKeys == Keys.Alt && ctr == null)
{
ctr = true;
rotate = new PointF((e.X - image.X) / zoom, (e.Y - image.Y) / zoom);
return;
}
pan = true;
mouse = e.Location;
_image = image;
}
private void mouseMove(object sender, MouseEventArgs e)
{
mcurrent = e.Location;
label();
if (e.Button != MouseButtons.Left || !pan) return;
image.X = _image.X + e.X - mouse.X;
image.Y = _image.Y + e.Y - mouse.Y;
image = new PointF(image.X, image.Y);
pbx.Invalidate();
}
private void mouseUp(object sender, MouseEventArgs e)
{
pan = false;
}
private void pbx_Paint(object sender, PaintEventArgs e)
{
label();
// Generate bitmap "bmp" - this can be saved as drawn...if deisred
bmp = new Bitmap(img.Width, img.Height);
using (Graphics g = Graphics.FromImage(bmp))
{
Matrix transform = new Matrix();
transform.Scale(zoom, zoom, MatrixOrder.Append);
transform.RotateAt(ang, rotate);
transform.Translate(image.X, image.Y, MatrixOrder.Append);
g.Transform = transform;
g.DrawImage(img, 0, 0);
}
e.Graphics.DrawImage(bmp, 0, 0);
}
}
}

Xamarin Forms PanGesture has inconsequent coordinates

I have a problem. I created an image within a AbsoluteLayout with a panGestureRecognizer, but when I use that to move the image in the app, it jumps back and forth. Very annoying. Here is the code I am using
private void AddImageToPreview(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e)
{
if (e.Action == System.Collections.Specialized.NotifyCollectionChangedAction.Add)
{
var image = (Image)e.NewItems[e.NewItems.Count - 1];
PanGestureRecognizer panGesture = new PanGestureRecognizer();
panGesture.PanUpdated += PanUpdated;
image.GestureRecognizers.Add(panGesture);
MyLayout.Children.Add(image);
}
}
void PanUpdated(object sender, PanUpdatedEventArgs args)
{
Image image = (Image)sender;
if (args.StatusType.Equals(GestureStatus.Running))
{
x = args.TotalX;
y = args.TotalY;
image.TranslateTo(x, y, 1);
}
}
Can someone help me improve this, so this drag/drop system works smooth and fast!

I have a control purely made in Xamarin.Forms that you can use for the above mentioned usage:
using System;
using Xamarin.Forms;
using FFImageLoading.Forms;
public class ZoomImage : CachedImage
{
private const double MIN_SCALE = 1;
private const double MAX_SCALE = 4;
private const double OVERSHOOT = 0.15;
private double StartScale, LastScale;
private double StartX, StartY;
public ZoomImage()
{
var pinch = new PinchGestureRecognizer();
pinch.PinchUpdated += OnPinchUpdated;
GestureRecognizers.Add(pinch);
var pan = new PanGestureRecognizer();
pan.PanUpdated += OnPanUpdated;
GestureRecognizers.Add(pan);
var tap = new TapGestureRecognizer { NumberOfTapsRequired = 2 };
tap.Tapped += OnTapped;
GestureRecognizers.Add(tap);
Scale = MIN_SCALE;
TranslationX = TranslationY = 0;
AnchorX = AnchorY = 0;
}
protected override SizeRequest OnMeasure(double widthConstraint, double heightConstraint)
{
Scale = MIN_SCALE;
TranslationX = TranslationY = 0;
AnchorX = AnchorY = 0;
return base.OnMeasure(widthConstraint, heightConstraint);
}
private void OnTapped(object sender, EventArgs e)
{
if (Scale > MIN_SCALE)
{
this.ScaleTo(MIN_SCALE, 250, Easing.CubicInOut);
this.TranslateTo(0, 0, 250, Easing.CubicInOut);
}
else
{
AnchorX = AnchorY = 0.5; //TODO tapped position
this.ScaleTo(MAX_SCALE, 250, Easing.CubicInOut);
}
}
private void OnPanUpdated(object sender, PanUpdatedEventArgs e)
{
switch (e.StatusType)
{
case GestureStatus.Started:
StartX = (1 - AnchorX) * Width;
StartY = (1 - AnchorY) * Height;
break;
case GestureStatus.Running:
AnchorX = Clamp(1 - (StartX + e.TotalX) / Width, 0, 1);
AnchorY = Clamp(1 - (StartY + e.TotalY) / Height, 0, 1);
break;
}
}
private void OnPinchUpdated(object sender, PinchGestureUpdatedEventArgs e)
{
switch (e.Status)
{
case GestureStatus.Started:
LastScale = e.Scale;
StartScale = Scale;
AnchorX = e.ScaleOrigin.X;
AnchorY = e.ScaleOrigin.Y;
break;
case GestureStatus.Running:
if (e.Scale < 0 || Math.Abs(LastScale - e.Scale) > (LastScale * 1.3) - LastScale)
{ return; }
LastScale = e.Scale;
var current = Scale + (e.Scale - 1) * StartScale;
Scale = Clamp(current, MIN_SCALE * (1 - OVERSHOOT), MAX_SCALE * (1 + OVERSHOOT));
break;
case GestureStatus.Completed:
if (Scale > MAX_SCALE)
this.ScaleTo(MAX_SCALE, 250, Easing.SpringOut);
else if (Scale < MIN_SCALE)
this.ScaleTo(MIN_SCALE, 250, Easing.SpringOut);
break;
}
}
private T Clamp<T>(T value, T minimum, T maximum) where T: IComparable
{
if (value.CompareTo(minimum) < 0)
return minimum;
else if (value.CompareTo(maximum) > 0)
return maximum;
else
return value;
}
}
What this does:
Pinch zoom, Pan and Swipe movements together with double tap centre zoom and un-zoom
Note: I have used FFimageLoading's CachedImage because I needed to cache the data in case you do not intend this replace CachedImage with Xamarin.Forms.Image

Losing correct position by zooming in c#

I have a image in a picture box.it contains a Triangle.
I have a another picture box that contain a little Circle. i should put Circle on top of Triangle . i Zoom first image(Triangle ) to find top of it and then put Circle there.i do it correctly . but when i reset zoom , top of Triangle will be lose and Circle will be on a wrong position.
my code for zoom:
protected override void OnMouseWheel(MouseEventArgs e)
{
this.Cursor = Cursors.Default;
float oldzoom = zoom;
if (e.Delta > 0)
{
zoom += 0.625f;
zoomPerectNum += 50;
_txt_precentZoom.Text = zoomPerectNum.ToString() + "%";
}
else if (e.Delta < 0)
{
// zoom = Math.Max(zoom - 1F, 1F);
zoom = zoom - 0.625F;
if (zoom < 0.2503874F)
{
zoom = 0.2503874F;
}
else
{
zoomPerectNum -= 50;
_txt_precentZoom.Text = zoomPerectNum.ToString() + "%";
}
}
MouseEventArgs mouse = e as MouseEventArgs;
Point mousePosNow = mouse.Location;
int x = mousePosNow.X - _pic_image.Location.X; // Where location of the mouse in the pictureframe
int y = mousePosNow.Y - _pic_image.Location.Y;
int oldimagex = (int)(x / oldzoom); // Where in the IMAGE is it now
int oldimagey = (int)(y / oldzoom);
int newimagex = (int)(x / zoom); // Where in the IMAGE will it be when the new zoom i made
int newimagey = (int)(y / zoom);
imgx = newimagex - oldimagex + imgx; // Where to move image to keep focus on one point
imgy = newimagey - oldimagey + imgy;
_pic_image.Refresh(); // calls imageBox_Paint
}
private void imageBox_Paint(object sender, PaintEventArgs e)
{
e.Graphics.InterpolationMode = InterpolationMode.HighQualityBicubic;
e.Graphics.ScaleTransform(zoom, zoom);
if (img != null)
{
e.Graphics.DrawImage(img, imgx, imgy);
}
}
_pic_Circle:
private void _pic_Circle_MouseDown(object sender, MouseEventArgs e)
{
dragging = true;
dragPoint = new Point(e.X, e.Y);
}
private void _pic_Circle_MouseMove(object sender, MouseEventArgs e)
{
if (dragging)
{
_pic_Circle.Location = new Point(_pic_Circle.Location.X + e.X - dragPoint.X, _pic_Circle.Location.Y + e.Y - dragPoint.Y);
}
}
private void _pic_Circle_MouseUp(object sender, MouseEventArgs e)
{
dragging = false;
}