gd-png: fatal libpng error: zlib error

The third parameter is for the quality of the image. 正在生成的图像是可能的最高质量的JPEG图像是一个范围从0（最低质量，最小的文件大小）到100（最高质量，最大文件大小）。 The images being generated are the highest quality possible which for JPEG images is a range from 0 (lowest quality, smallest file size) to 100 (highest quality, largest file size).

出现这一错误的原因是为ImagePNG职能的质量范围从0到9的任何外部不会工作。 The reason for the error is that the quality range for the ImagePNG function is from 0 to 9 and anything outside that won't work. 所以，简单地将值更改为0到9之间，错误会自行消失。 So simply change the value to between 0 and 9 and the error will go away.