通过文件二进制信息判断图片类型(png,jpg,gif)

1. package lab.sodino.img;
2. import java.io.IOException;
3. import java.io.InputStream;
4. import javax.microedition.io.Connector;
5. import javax.microedition.io.file.FileConnection;
6. import javax.microedition.midlet.MIDlet;
7. import javax.microedition.midlet.MIDletStateChangeException;
8. /** @author sodino */
9. public class ImgTypeextends MIDlet {
10. public ImgType() {
11. }
12. protected void destroyApp(boolean arg0)throws MIDletStateChangeException {
13. }
14. protected void pauseApp() {
15. }
16. protected void startApp()throws MIDletStateChangeException {
17. String prefix = "file:///root1/";
18. // testFile(prefix + "logo_cn.gif");
19. // testFile(prefix + "04.jpg");
20. testFile(prefix + "img.png");
21. }
22. public void testFile(String url) {
23. try {
24. int length = 10;
25. FileConnection fc = (FileConnection) Connector.open(url);
26. InputStream is = fc.openInputStream();
27. byte[] data = new byte[length];
28. is.read(data);
29. String type = getType(data);
30. System.out.println(url + " is " + type);
31. is.close();
32. fc.close();
33. } catch (IOException e) {
34. e.printStackTrace();
35. }
36. }
37. public String getType(byte[] data) {
38. String type = null;
39. // Png test:
40. if (data[1] == 'P' && data[2] == 'N' && data[3] =='G') {
41. type = "PNG";
42. return type;
43. }
44. // Gif test:
45. if (data[0] =='G' && data[1] == 'I' && data[2] == 'F') {
46. type = "GIF";
47. return type;
48. }
49. // JPG test:
50. if (data[6] == 'J' && data[7] == 'F' && data[8] =='I'
51. && data[9] == 'F') {
52. type = "JPG";
53. return type;
54. }
55. return type;
56. }
57. }

package lab.sodino.img;import java.io.IOException;import java.io.InputStream;import javax.microedition.io.Connector;import javax.microedition.io.file.FileConnection;import javax.microedition.midlet.MIDlet;import javax.microedition.midlet.MIDletStateChangeException;/** @author sodino */public class ImgType extends MIDlet {public ImgType() {}protected void destroyApp(boolean arg0) throws MIDletStateChangeException {}protected void pauseApp() {}protected void startApp() throws MIDletStateChangeException {String prefix = "file:///root1/";// testFile(prefix + "logo_cn.gif");// testFile(prefix + "04.jpg");testFile(prefix + "img.png");}public void testFile(String url) {try {int length = 10;FileConnection fc = (FileConnection) Connector.open(url);InputStream is = fc.openInputStream();byte[] data = new byte[length];is.read(data);String type = getType(data);System.out.println(url + " is " + type);is.close();fc.close();} catch (IOException e) {e.printStackTrace();}}public String getType(byte[] data) {String type = null;// Png test:if (data[1] == 'P' && data[2] == 'N' && data[3] == 'G') {type = "PNG";return type;}// Gif test:if (data[0] == 'G' && data[1] == 'I' && data[2] == 'F') {type = "GIF";return type;}// JPG test:if (data[6] == 'J' && data[7] == 'F' && data[8] == 'I'&& data[9] == 'F') {type = "JPG";return type;}return type;}}