How do I specify the size of this gd database function?

I read this
http://yuncode.net/code/c_594.
is successful after using it. It doesn"t seem to be misused, and it doesn"t seem to have a bad effect.
it"s just a little more skeptical

.

question 1
this is to multiply the height by 0.9 if you exceed the 600x600, and directly discount by 10%.
is it possible to "specify the degree and height"? Suppose I want 550x250?
Chong Chong: I found it integrated into 

$new_width = 550;
$new_height = 250;

will not flatten the film in an equal proportion, but directly flatten our film.
original:

clipboard.png

:

clipboard.png

question 2 

 //75
imagejpeg($image_wp, $imgdst,75);

I don"t quite understand this sentence, so what does the number 75 stand for? The lower it is, the more arrogant it is. The smaller the file size?

question 3
are both jpg and jpeg processed at case 2: ?

question 4
is there a more appropriate function to upgrade this function? To make it more efficient? This kind of thing. Curiously, the article has been published for more than a year

.

question 5
what can I do if the film is lower than the height I specified? On the contrary, it is said that it will increase size

.
Php php7 gd gd-Library
Jun.10,2021

problem 1:imagecopyresampled can use this function to enlarge and shrink the picture to a specified scale and will not compress (but only to a ratio equal to the original image)
problem 2:70 represents the quality value of the picture, the lower the compression, the more severe the compression, but this only has
question 3: yes, because this is the same type of
question 4: this is basically the most concise way. Because the basis of further upgrade is also these methods
question 5: if it is lower than the width and height you specify, you can enlarge it according to the proportional value

in the original text 
   


 in addition, if you want to study php image processing, you should take a look at the imagemagick documentation 
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MySQL Query : SELECT * FROM `codeshelper`.`v9_news` WHERE status=99 AND catid='6' ORDER BY rand() LIMIT 5
MySQL Error : Disk full (/tmp/#sql-temptable-64f5-1e9b6c4-4760f.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
MySQL Errno : 1021
Message : Disk full (/tmp/#sql-temptable-64f5-1e9b6c4-4760f.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
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