解码 JPEG 文件时跨浏览器不兼容？

Question

有些事情让我感到困惑 - 为什么 this image在每个浏览器中显示不同？

IE9(和 Windows 照片查看器)中的图像:


Firefox(和 Photoshop)中的图像:


Chrome(和 Irfanview)中的图像:


他们对 JPEG 的解码过程中发生了什么使最终输出如此不同？

(在 IE、Firefox、Chrome 等中查看以了解我的意思。)

Answer 1

JPEGSnoop (源现在可用@ sourceforge)在我们甚至在进行 Y'CbCr 到 RGB 转换之前就报告了大量的亮度溢出。我在其他一些文件上遇到这些错误，但溢出通常很小 - 256 或 257，而最大值为 255。此处计算的亮度为 729!

JPEGSnoop 的作者对 YCC 溢出的评论:

YCC clipping in DC - Each MCU adds or subtracts from the DC (average) value in the previous MCU. These should all stay within an 8-bit range, but corruption in the DC coefficient may cause this value to wander out of range. This type of error will cause sudden large-scale changes in color or brightness in your image. As this type of error generally won't recover, JPEGsnoop will only report the first 10 of these in the log file.

我不熟悉跨 MCU DC，但 Pennebaker & Mitchel concur .

*** Decoding SCAN Data ***
  OFFSET: 0x00000160
  Scan Decode Mode: Full IDCT (AC + DC)

  Scan Data encountered marker   0xFFD9 @ 0x00027CA9.0

*** NOTE: YCC Clipped. MCU=(   0,   0) YCC=(  729,  109,  171) Y Overflow @ Offset 0x00027CA8.2
*** NOTE: YCC Clipped. MCU=(   0,   0) YCC=(  682,  109,  172) Y Overflow @ Offset 0x00027CA8.2
*** NOTE: YCC Clipped. MCU=(   0,   0) YCC=(  741,  109,  173) Y Overflow @ Offset 0x00027CA8.2
*** NOTE: YCC Clipped. MCU=(   0,   0) YCC=(  629,  109,  174) Y Overflow @ Offset 0x00027CA8.2
*** NOTE: YCC Clipped. MCU=(   0,   0) YCC=(  841,  109,  175) Y Overflow @ Offset 0x00027CA8.2
*** NOTE: YCC Clipped. MCU=(   0,   0) YCC=(  319,  109,  176) Y Overflow @ Offset 0x00027CA8.2
*** NOTE: YCC Clipped. MCU=(   0,   0) YCC=(  928,  109,  177) Y Overflow @ Offset 0x00027CA8.2
*** NOTE: YCC Clipped. MCU=(   0,   0) YCC=(  624,  109,  177) Y Overflow @ Offset 0x00027CA8.2
*** NOTE: YCC Clipped. MCU=(   1,   0) YCC=(  785,  107,  171) Y Overflow @ Offset 0x00027CA8.2
*** NOTE: YCC Clipped. MCU=(   1,   0) YCC=(  559,  107,  171) Y Overflow @ Offset 0x00027CA8.2
    Only reported first 10 instances of this message...