java ImageIO.write() 方法和 png
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ImageIO.write() method and png
提问by blue
Why ImageIO.write(bufferedimage_dest,"png",new File(filedest));writes jpg (without transparency colour) file instead png?
为什么ImageIO.write(bufferedimage_dest,"png",new File(filedest));写 jpg（没有透明颜色）文件而不是 png？
Added:
添加：
static BufferedImage createResizedCopy(Image originalImage,
int scaledWidth, int scaledHeight,
boolean preserveAlpha)
{
System.out.println("resizing...");
int imageType = preserveAlpha ? BufferedImage.TYPE_INT_RGB : BufferedImage.TYPE_INT_ARGB;
BufferedImage scaledBI = new BufferedImage(scaledWidth, scaledHeight, imageType);
Graphics2D g = scaledBI.createGraphics();
if (preserveAlpha) {
g.setComposite(AlphaComposite.Src);
}
g.drawImage(originalImage, 0, 0, scaledWidth, scaledHeight, null);
g.dispose();
return scaledBI;
}
public static void scale(String src, int width, int height, String dest)
throws IOException {
BufferedImage bsrc = ImageIO.read(new File(src));
BufferedImage bdest =
new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);
bdest = createResizedCopy(bsrc, width, height, false);
ImageIO.write(bdest,"png",new File(dest));
}
Added:
添加：
well, in main() function I've called
好吧，在我调用的 main() 函数中
ScaleJPG.scale((args[0],Integer.parseInt(args[1]),Integer.parseInt(args[2]), args[3]););
instead of
代替
ScalePNG.scale((args[0],Integer.parseInt(args[1]),Integer.parseInt(args[2]), args[3]););
ScaleJPG was similiar, previous class in this folder.
ScaleJPG 与此文件夹中的先前类类似。
I must discard notepad and use only IDE. Question to delete.
我必须丢弃记事本并仅使用 IDE。要删除的问题。
采纳答案by Serhiy
Add
添加
g.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR);
before g.drawImage(originalImage, 0, 0, scaledWidth, scaledHeight, null);to the createResizedCopyfunction.
之前g.drawImage(originalImage, 0, 0, scaledWidth, scaledHeight, null);的createResizedCopy功能。
回答by Bozho
You need your buffered image to have an image type of BufferedImage.TYPE_INT_ARGB
您需要缓冲图像的图像类型为 BufferedImage.TYPE_INT_ARGB
回答by Joachim Sauer
It does not. This simple test class verifies it:
它不是。这个简单的测试类验证了它：
import java.awt.image.*;
import java.io.File;
import javax.imageio.*;
public class Main
{
public static void main (String [] args) throws Exception
{
BufferedImage bi = new BufferedImage(100,100,BufferedImage.TYPE_INT_ARGB);
ImageIO.write(bi, "png", new File("test.png"));
}
}
Compiling and executing it produces a .png file just as expected:
正如预期的那样，编译并执行它会生成一个 .png 文件：
$ javac Main.java $ java Main $ file test.png test.png: PNG image, 100 x 100, 8-bit/color RGBA, non-interlaced $
