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HTML5 Canvas distorted
HTML5 Canvas distortion occurs when the canvas element's CSS dimensions don't match its internal drawing dimensions. This creates scaling issues that make drawings appear stretched or blurry.
Understanding Canvas Dimensions
Canvas has two sets of dimensions:
-
Drawing dimensions: Set via
widthandheightattributes -
Display dimensions: Set via CSS
widthandheightproperties
When these don't match, the browser scales the drawing surface to fit the display size, causing distortion.
Default Canvas Size
The default canvas dimensions are:
width = 300px height = 150px
This gives a 2:1 aspect ratio. If you don't specify dimensions, the canvas uses these defaults.
Correct Way to Set Canvas Size
Always set dimensions using HTML attributes, not CSS:
<!DOCTYPE html>
<html>
<head>
<style>
#canvas1 { border: 1px solid red; }
</style>
</head>
<body>
<canvas id="canvas1" width="400" height="300"></canvas>
<script>
const canvas = document.getElementById('canvas1');
const ctx = canvas.getContext('2d');
// Draw a circle to test distortion
ctx.beginPath();
ctx.arc(200, 150, 50, 0, 2 * Math.PI);
ctx.fillStyle = 'blue';
ctx.fill();
ctx.stroke();
</script>
</body>
</html>
Common Distortion Issues
| Problem | Cause | Solution |
|---|---|---|
| Blurry drawings | CSS scaling | Match HTML and CSS dimensions |
| Stretched shapes | Aspect ratio mismatch | Use consistent width/height ratios |
| Pixelated graphics | Small drawing surface | Increase canvas width/height attributes |
Setting Canvas Size Programmatically
<!DOCTYPE html>
<html>
<body>
<canvas id="mycanvas"></canvas>
<script>
const canvas = document.getElementById('mycanvas');
// Set both drawing and display dimensions
canvas.width = 400;
canvas.height = 300;
canvas.style.width = '400px';
canvas.style.height = '300px';
canvas.style.border = '1px solid red';
const ctx = canvas.getContext('2d');
ctx.fillRect(50, 50, 100, 100);
console.log('Canvas dimensions set programmatically');
</script>
</body>
</html>
Conclusion
To avoid canvas distortion, always set dimensions using HTML attributes rather than CSS. Ensure drawing dimensions match display dimensions for crisp, undistorted graphics.
Updated on: 2026-03-15T23:18:59+05:30
747 Views
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