如何在Android中使彩色图像变为黑白
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how to make the color image to black and white in Android
提问by lakshman
I wanted to know the way to convert the color image (which i am downloading from net) to black and white when i am displaying it to the user in android. can anybody found this requirement in any of your android work. Please let me know.
我想知道当我在 android 中向用户显示彩色图像（我从网上下载）转换为黑白的方法。任何人都可以在您的任何 android 工作中找到这个要求。请告诉我。
Thanks Lakshman
谢谢拉克什曼
回答by Munish Kapoor
Hi you can make the image black n white using contrast.
嗨，您可以使用对比度使图像变黑变白。
See the code..
看代码。。
public static Bitmap createContrast(Bitmap src, double value) {
// image size
int width = src.getWidth();
int height = src.getHeight();
// create output bitmap
Bitmap bmOut = Bitmap.createBitmap(width, height, src.getConfig());
// color information
int A, R, G, B;
int pixel;
// get contrast value
double contrast = Math.pow((100 + value) / 100, 2);
// scan through all pixels
for(int x = 0; x < width; ++x) {
for(int y = 0; y < height; ++y) {
// get pixel color
pixel = src.getPixel(x, y);
A = Color.alpha(pixel);
// apply filter contrast for every channel R, G, B
R = Color.red(pixel);
R = (int)(((((R / 255.0) - 0.5) * contrast) + 0.5) * 255.0);
if(R < 0) { R = 0; }
else if(R > 255) { R = 255; }
G = Color.red(pixel);
G = (int)(((((G / 255.0) - 0.5) * contrast) + 0.5) * 255.0);
if(G < 0) { G = 0; }
else if(G > 255) { G = 255; }
B = Color.red(pixel);
B = (int)(((((B / 255.0) - 0.5) * contrast) + 0.5) * 255.0);
if(B < 0) { B = 0; }
else if(B > 255) { B = 255; }
// set new pixel color to output bitmap
bmOut.setPixel(x, y, Color.argb(A, R, G, B));
}
}
return bmOut;
}
Set the double value to 50 on mathod call. For Example createContrast(Bitmap src, 50)
在 mathod 调用中将 double 值设置为 50。例如createContrast(Bitmap src, 50)
回答by lenooh
Use the built-in methods:
使用内置方法：
public static Bitmap toGrayscale(Bitmap srcImage) {
Bitmap bmpGrayscale = Bitmap.createBitmap(srcImage.getWidth(), srcImage.getHeight(), Bitmap.Config.ARGB_8888);
Canvas canvas = new Canvas(bmpGrayscale);
Paint paint = new Paint();
ColorMatrix cm = new ColorMatrix();
cm.setSaturation(0);
paint.setColorFilter(new ColorMatrixColorFilter(cm));
canvas.drawBitmap(srcImage, 0, 0, paint);
return bmpGrayscale;
}
