图片压缩有什么坏处,如何将图片改为jpg

publicstaticvoidreduceimg (string img src，String imgdist，int widthdist，int heightdist ) try{filesrcfile=newfile ) img srch srcfile.exists () ) { return； } image src=javax.imageio.imageio.read (srcfile )； bufferedimagetag=newbufferedimage () int (width dist，) int (height dist，BufferedImage.TYPE_INT_RGB )； tag.get graphics (.drawimage (src.getscaledinstance ) widthdist，heightdist，Image.SCALE_SMOOTH )，0，nullllaphich nu//tag.get graphics (.drawimage (src.getscaledinstance ) widthdist，heightdist，image.scale _ area _ averaginnge 精力充沛的海豚=JPEG codec.createjpegencoder (out )； encoder.encode(tag； out.close (； }catch(ioexceptionex ) { ex.printStackTrace )； }