用canvas實現圖片濾鏡效果詳解之灰度效果

for ( var x = 0; x < canvasData.width; x++) {
for ( var y = 0; y < canvasData.height; y++) {

// Index of the pixel in the array
 var idx = (x + y * canvasData.width) * 4;
 var r = canvasData.data[idx + 0];
 var g = canvasData.data[idx + 1];
 var b = canvasData.data[idx + 2];
 var gray = .299 * r + .587 * g + .114 * b;

// assign gray scale value
 canvasData.data[idx + 0] = gray; // Red channel
 canvasData.data[idx + 1] = gray; // Green channel
 canvasData.data[idx + 2] = gray; // Blue channel
 canvasData.data[idx + 3] = 255; // Alpha channel
// 加上黑色的邊框
if(x < 8 || y < 8 || x > (canvasData.width - 8) || y > (canvasData.height - 8))
 {
 canvasData.data[idx + 0] = 0;
 canvasData.data[idx + 1] = 0;
 canvasData.data[idx + 2] = 0;
 }
 }
}

3.把新的圖像數據寫入canvas

context.putImageData(canvasData, 0, 0);

4.效果預覽

點這裏看預覽