Someone once gave me a jpg, which is 1024*1024 size, with a file size of 99kb, and made a pyramid. The image sizes of each layer are as follows: unit kb
The jpg pyramid I generated is for any processing
height256 46.2kb
height512 162kb
height1024 557kb
Photoshop generated jpg pyramid is processed for any processing
height256 48kb
height512 90kb
height1024 163kb
It can be seen that the size difference of this image is too big, but I can't figure it out. Finally, after reading the above blog post, I took a look at the reason by obtaining metadata:
Get metadata function
public void GetProperty()
{
Bitmap myImage1024 = new Bitmap(@"E:\myjpg\");
foreach (PropertyItem property in )
{
StringBuilder sb=new StringBuilder();
Byte[] sbbyte = (Byte[]);
("ID:{0},Length:{1},Type:{2};\n",
(), (), (),);
(sb);
}
}
I found that the metadata of the jpg I generated and the original image are different
height1024：
ID:771,Length:1,Type:1; Header information Tag explanation: 303 PropertyTagSRGBRenderingIntent
ID:769,Length:8,Type:5; Header information Tag explanation: 301 PropertyTagGamma
ID:20752,Length:1,Type:1; Header information Tag explanation: 5110 PropertyTagPixelUnit resolution
ID:20753,Length:4,Type:4; Header information Tag explanation: 5111 PropertyTagPixelPerUnitX
ID:20754,Length:4,Type:4; Header information Tag explanation: 5112 PropertyTagPixelPerUnitY
height：
ID: 20625,Length:128,Type:3;Head information Tag explanation: 5091 PropertyTagChrominanceTable
ID:20624,Length:128,Type:3; Header information Tag explanation: 5090 PropertyTagLuminanceTable
So that's it, so we know why jpg is different in size. Well, I modified the method of generating image pyramids: remove their header information before saving the pyramids. Later, I was surprised to find that the finest layer of the image pyramid I generated was the same size as the original image! .
How to remove image metadata:
public void RemoveProperty()
{
Bitmap myImage1024 = new Bitmap(@"E:\myjpg\");
foreach (PropertyItem property in )
{
();
}
(@"E:\myjpg\");
}