轉換JPG至PNG背景透明

Question

雖然從JPG轉換成PNG背景透明度的形象，我不希望在轉換圖像的虛線邊框

我原來的圖片（JPG）

我變換後的圖像（PNG）

我的源代碼是

import java.awt.Color; 
import java.awt.Graphics2D; 
import java.awt.Image; 
import java.awt.Toolkit; 
import java.awt.image.BufferedImage; 
import java.awt.image.FilteredImageSource; 
import java.awt.image.ImageFilter; 
import java.awt.image.ImageProducer; 
import java.awt.image.RGBImageFilter; 
import java.io.File; 

import javax.imageio.ImageIO; 

public class DemoTransparent { 

    public static void main(String[] args) throws Exception { 

     URL url = new URL("http://i.stack.imgur.com/jEqbx.jpg"); 
     Image image1 = ImageIO.read(url); 
     BufferedImage source = (BufferedImage) image1; 
     int color = source.getRGB(0, 0); 
     Image image = makeColorTransparent(source, new Color(color)); 
     BufferedImage transparent = imageToBufferedImage(image); 
     File out = new File("D:\\Demo.png"); 
     ImageIO.write(transparent, "PNG", out); 

    } 

    private static BufferedImage imageToBufferedImage(Image image) { 

     BufferedImage bufferedImage = new BufferedImage(image.getWidth(null), image.getHeight(null), BufferedImage.TYPE_4BYTE_ABGR_PRE); 

     Graphics2D g2 = bufferedImage.createGraphics(); 
     g2.drawImage(image, 0, 0, null); 
     g2.dispose(); 
     return bufferedImage; 

    } 

    public static Image makeColorTransparent(BufferedImage im, final Color color) { 
     ImageFilter filter = new RGBImageFilter() { 

      public int markerRGB = color.getRGB() | 0xFF000000; 
      public final int filterRGB(int x, int y, int rgb) { 
       if ((rgb | 0xFF000000) == markerRGB) { 
        return 0x00FFFFFF & rgb; 
       } else { 
        return rgb; 
       } 
      } 


     }; 
     ImageProducer ip = new FilteredImageSource(im.getSource(), filter); 
     return Toolkit.getDefaultToolkit().createImage(ip); 
    } 

} 

我只想爲png透明背景圖片

Answer 1

通常我們做什麼來提取顏色正好等於或幾乎等於一個顏色是需要的閾值。

這裏是你的代碼的小修改：

// Take another parameter i.e. threshold 
public static Image makeColorTransparent(BufferedImage im, final Color color, float threshold) { 
    ImageFilter filter = new RGBImageFilter() { 
     public float markerAlpha = color.getRGB() | 0xFF000000; 
     public final int filterRGB(int x, int y, int rgb) { 
      int currentAlpha = rgb | 0xFF000000;   // just to make it clear, stored the value in new variable 
      float diff = Math.abs((currentAlpha - markerAlpha)/markerAlpha); // Now get the difference 
      if (diff <= threshold) {      // Then compare that threshold value 
       return 0x00FFFFFF & rgb; 
      } else { 
       return rgb; 
      } 
     } 
    }; 
    ImageProducer ip = new FilteredImageSource(im.getSource(), filter); 
    return Toolkit.getDefaultToolkit().createImage(ip); 
} 

然後調用功能makeColorTransparent(image, color, 0.05f);
但在你的形象問題。橢圓角上的像素顏色與橢圓內部的像素顏色（右下角）完全相同。所以算法也在消除這些像素。

可悲的是，你不能包括這些像素。我試圖用不同的閾值來做到這一點。但是，無論是角落包括或橢圓形的一些像素被刪除。你可以做的是使用0.05f作爲閾值，然後用手繪製你想要的區域（使用photoshop或任何簡單的圖像編輯器）。