反转位图图像会使图像变黑。但前后不一致

【问题标题】：Inverting bitmap image turns the image black. But inconsistently反转位图图像会使图像变黑。但前后不一致
【发布时间】：2014-11-25 08:32:26
【问题描述】：

我正在尝试用一些用 C 编写的代码来否定位图图像。

  1. 当我第一次运行 Lena 图像（让我称之为 LenaImage1）的代码时，我得到一个黑色图像 (LenaImage2)。当我在图像上运行相同的代码时，我会取回原始图像（LenaImage1）。这意味着代码可以正常工作吗？ 当我使用 MATLAB 查看和保存（作为位图）LenaImage2 时，我没有得到黑色图像，这意味着我可以将其视为补充图像（MATLAB 返回相同的输出）。

  2. 当我在第二张图像 (MountainImage1) 上运行相同的 C 代码时，我得到一个非常糟糕的图像 (MounainImage2)，其中有很多伪着色，但不是黑色图像作为输出。当我在 MATLAB 中运行代码来赞美 MounainImage1 时，我得到了看起来像正确图像但没有伪着色的图像。当我在 MountainImage2 上运行 C 代码时，我得到了原始图像（即 MountainImage1）。

在第三张图像上运行代码会显示类似于 Lena 图像的行为。所有提到的图片都可以在here找到。

另一个answer 提到位图图像不支持透明度。

我在这里看到的是透明度问题吗？ 如果是，为什么我没有在所有图像中看到此透明度问题的一致行为？ 另外，当我使用 MATLAB 查看和保存 LenaImage2 以及 MountainImage2 时，它没有显示黑色图像或任何伪着色，这是怎么回事？ 如何更正我的 C 代码？

这是反转图像的代码：

我的头文件中的文件头声明：

            #pragma pack(push,1)
            typedef struct bmpFileHeader
            {
                unsigned short bfType;       /*specifies the file type*/
                unsigned long bfSize;        /*specifies the size in bytes of the bitmap file*/
                unsigned short bfReserved1;  /*reserved; must be 0*/
                unsigned short bfReserved2;  /*reserved; must be 0*/
                unsigned long bfOffBits;     /*species the offset in bytes from the bitmapfileheader to the bitmap bits*/
            }bmpFileHeader;

            typedef struct bmpInfoHeader
            {
                unsigned long biSize;           /*Size of bmpInfoHeader*/
                unsigned long biWidth;          /*specifies width in pixels*/
                unsigned long biHeight;         /*species height in pixels*/
                unsigned short biPlanes;        /*specifies the number of color planes, must be 1*/
                unsigned short biBitCount;      /*specifies the number of bit per pixel*/
                unsigned long biCompression;    /*spcifies the type of compression*/
                unsigned long biSizeImage;      /*size of image in bytes*/
                unsigned long biXPelsPerMeter;  /*number of pixels per meter in x axis*/
                unsigned long biYPelsPerMeter;  /*number of pixels per meter in y axis*/
                unsigned long biClrUsed;        /*number of colors used by the bitmap*/
                unsigned long biClrImportant;   /*number of colors that are important*/
            }bmpInfoHeader;
            #pragma pack(pop)

完成工作的代码：

            void ImageData(FILE *filePtr)
            {
                bmpFileHeader FileHeader;
                bmpInfoHeader InfoHeader;
                char *bmpImageData;    /*array to hold the image data*/
                size_t imagedataSize=0,check=0;
                int y;


                /*read the bitmap file header*/
                check=fread(&FileHeader, sizeof(bmpFileHeader),1,filePtr);
                printf("checkFileHeader=%d\n",check);

                /*verify that this is a bmp file by check bitmap id*/
                if (FileHeader.bfType !=0x4D42)
                {
                    fclose(filePtr);
                    printf("ImageData:Is not a BMP file\n");
                    return;
                }

                /*read the bitmap info header*/
                check=fread(&InfoHeader, sizeof(InfoHeader),1,filePtr);
                printf("checkInfoHeader=%d\n",check);

                /*Allocate space for the image data*/

                bmpImageData=(char*)malloc(InfoHeader.biSizeImage);
                if(bmpImageData==NULL){
                    printf("Couldn't allocate memory for ImageData\n");
                    return;
                }
                /*move the file position to the point where the aligned image data begins*/
                check=fseek(filePtr,FileHeader.bfOffBits,SEEK_SET);
                if(check!=0){
                    printf("Error seeking file\n");
                    return;
                }
                /*Copy the image data to bmpImageData*/
                check=fread(bmpImageData,InfoHeader.biSizeImage,1,filePtr);
                if(check!=1){
                    printf("Error reading image data\n");
                    return
                }

                /*Moving filePtr to position where image data begins*/
                check=fseek(filePtr,FileHeader.bfOffBits,SEEK_SET);
                if(check!=0){
                    printf("Error seeking file\n");
                    return;
                }
                /*Manipulating the image data*/
                for(y=0;y<InfoHeader.biSizeImage;y++){
                    bmpImageData[y]=255-bmpImageData[y];
                }
                check=fwrite(bmpImageData,InfoHeader.biSizeImage,1,filePtr);
                if(check!=1)
                    printf("Error writing image data to file");

                free(bmpImageData);

            }

我使用的所有图像都是 8 位像素深度的灰度图像。我在 x86 机器上使用 CodeBlocks IDE（GNU GCC 编译器） 运行 Windows 8。

补充： 这是 Lena 图像的标题字段读取的内容：

            File Header Information
            FileHeaderSize=14
            bfType=4d42
            bfSize=263222
            bfReserved1=0
            bfReserved2=0
            bfOffBits=1078

            Info Header Information
            InfoHeaderSize=40
            biSize=40
            biHeight=512
            biWidth=512
            biPlanes=1
            biBitCount=8
            biCompression=0
            biSizeImage=262144
            biXPelsPerMeter=0
            biYPelsPerMeter=0
            biClrUsed=256
            biClrImportant=256

【问题讨论】：

  • 我对您要做什么没有高级别的概述，但您看起来好像被某种专有的、低效的（垃圾）Microsoft 文件格式纠缠不清。请看一下 Netpbm 的 PGM 格式（便携式灰度图），它支持 Matlab 和 MILES 更容易编程...en.wikipedia.org/wiki/Netpbm_format
  • 我去看看马克！谢谢！但是在我们的图像处理课程中，我们要编写 C 代码来处理 BMP 文件格式的图像，这就是为什么我现在必须限制自己。
  • 快速猜测：你的图像数据不应该是unsigned chars 而不是chars？
  • @M Oehm 我确实从unsigned char 开始，但后来将其更改为char 似乎在这里没有任何区别。输出确实保持不变。
  • 我没有 BMP 文档，但 bfOffBits 不是 54，biClrUsed 不是 0 的事实都是您拥有基于调色板的图像的线索。也就是说字节值不是灰度值。它们是调色板的索引。从 255 中减去会得到一个无意义的图像，但它是可逆的，因此您可以通过运行您的代码两次来恢复原始图像。

标签： c matlab image-processing bitmapimage


【解决方案1】：

bitcount=8，这意味着颜色表（调色板）是强制性的 - 请参阅here。这意味着像素数组中的值（即您的变量bmpImageData）不是颜色，而是实际上是调色板的索引。因此，您不能明智地直接修改bmpImageData。

因此，如果 pixel[0,0] 包含 3，您必须在调色板中查找第 3 个条目以计算出对应的颜色。

调色板应该在 BITMAPINFOHEADER 和 DIB 之后，所以它是从字节 55-435 开始的。

我建议您以十六进制打印出这些字节并查看它们。我猜你会看到它们是 RGBA、RGBA、RGBA，但 A（alpha 或透明度）将为零，即未使用。所以我希望它们看起来像这样，R=G=B（因为它们是灰度的）：

xx xx xx 00 yy yy yy 00 zz zz zz 00

然后，为了反转您的图像，将调色板中的每个xx 更改为255-xx（以及y 和z），而根本不需要处理所有bmpImageData。

我的回答有些不一致，但那是因为我在尝试调试BMP 文件时只能看到JPEG 文件。一个不一致的地方是 DIB 和像素阵列之间的空间是 436-54 字节，即 382 字节不能被 3 或 4 整除，因此对于每个条目使用 3 或 4 字节的调色板大小并不合理...但是获取十六进制数据，我们将看看是否可以更接近正确答案。

如果您使用 ImageMagick（可从 here 免费获得，适用于 Unix/Linux 和 Windows），您可以使用以下 identify 命令来帮助您调试代码：

  identify -verbose lena.bmp

  Format: BMP (Microsoft Windows bitmap image)
  Class: PseudoClass
  Geometry: 512x512+0+0
  Units: PixelsPerCentimeter
  Type: Grayscale
  Base type: Grayscale
  Endianess: Undefined
  Colorspace: Gray
  Depth: 8-bit
  Channel depth:
    gray: 8-bit
  Channel statistics:
    Pixels: 262144
    Gray:
      min: 28 (0.109804)
      max: 244 (0.956863)
      mean: 124.071 (0.486554)
      standard deviation: 47.9288 (0.187956)
      kurtosis: -0.839484
      skewness: -0.0822738
  Colors: 28
  Histogram:
       474: ( 28, 28, 28) #1C1C1C gray(28)
      4477: ( 36, 36, 36) #242424 gray(36)
     13395: ( 44, 44, 44) #2C2C2C gray(44)
     15131: ( 52, 52, 52) #343434 gray(52)
      9461: ( 60, 60, 60) #3C3C3C gray(60)
      6569: ( 68, 68, 68) #444444 gray(68)
      7027: ( 76, 76, 76) #4C4C4C gray(76)
      7733: ( 84, 84, 84) #545454 gray(84)
     10330: ( 92, 92, 92) #5C5C5C gray(92)
     14865: (100,100,100) #646464 gray(100)
     12095: (108,108,108) #6C6C6C gray(108)
     11631: (116,116,116) #747474 gray(116)
     16153: (124,124,124) #7C7C7C gray(124)
     17429: (132,132,132) #848484 gray(132)
     17623: (140,140,140) #8C8C8C gray(140)
     18636: (148,148,148) #949494 gray(148)
     19688: (156,156,156) #9C9C9C gray(156)
     12554: (164,164,164) #A4A4A4 gray(164)
      9848: (172,172,172) #ACACAC gray(172)
      7380: (180,180,180) #B4B4B4 gray(180)
      5589: (188,188,188) #BCBCBC gray(188)
      7162: (196,196,196) #C4C4C4 gray(196)
      7451: (204,204,204) #CCCCCC gray(204)
      6699: (212,212,212) #D4D4D4 gray(212)
      2293: (220,220,220) #DCDCDC gray(220)
       425: (228,228,228) #E4E4E4 gray(228)
        22: (236,236,236) #ECECEC gray(236)
         4: (244,244,244) #F4F4F4 gray(244)
  Colormap entries: 256
  Colormap:
         0: (  0,  0,  0) #000000 gray(0)
         1: (128,  0,  0) #800000 gray(128)
         2: (  0,128,  0) #008000 gray(0)
         3: (128,128,  0) #808000 gray(128)
         4: (  0,  0,128) #000080 gray(0)
         5: (128,  0,128) #800080 gray(128)
         6: (  0,128,128) #008080 gray(0)
         7: (128,128,128) #808080 gray(128)
         8: ( 28, 28, 28) #1C1C1C gray(28)
         9: (140,140,140) #8C8C8C gray(140)
        10: ( 84, 84, 84) #545454 gray(84)
        11: (196,196,196) #C4C4C4 gray(196)
        12: ( 60, 60, 60) #3C3C3C gray(60)
        13: (172,172,172) #ACACAC gray(172)
        14: (116,116,116) #747474 gray(116)
        15: (228,228,228) #E4E4E4 gray(228)
        16: ( 44, 44, 44) #2C2C2C gray(44)
        17: (156,156,156) #9C9C9C gray(156)
        18: (100,100,100) #646464 gray(100)
        19: (212,212,212) #D4D4D4 gray(212)
        20: ( 76, 76, 76) #4C4C4C gray(76)
        21: (188,188,188) #BCBCBC gray(188)
        22: (132,132,132) #848484 gray(132)
        23: (244,244,244) #F4F4F4 gray(244)
        24: ( 36, 36, 36) #242424 gray(36)
        25: (148,148,148) #949494 gray(148)
        26: ( 92, 92, 92) #5C5C5C gray(92)
        27: (204,204,204) #CCCCCC gray(204)
        28: ( 68, 68, 68) #444444 gray(68)
        29: (180,180,180) #B4B4B4 gray(180)
        30: (124,124,124) #7C7C7C gray(124)
        31: (236,236,236) #ECECEC gray(236)
        32: ( 52, 52, 52) #343434 gray(52)
        33: (164,164,164) #A4A4A4 gray(164)
        34: (108,108,108) #6C6C6C gray(108)
        35: (220,220,220) #DCDCDC gray(220)
        36: (  0,  0,  0) #000000 gray(0)
        37: (  0,  0,  0) #000000 gray(0)
        38: (  0,  0,  0) #000000 gray(0)
        39: (  0,  0,  0) #000000 gray(0)
        40: (  0,  0,  0) #000000 gray(0)
        41: (  0,  0,  0) #000000 gray(0)
        42: (  0,  0,  0) #000000 gray(0)
        43: (  0,  0,  0) #000000 gray(0)
        44: (  0,  0,  0) #000000 gray(0)
        45: (  0,  0,  0) #000000 gray(0)
        46: (  0,  0,  0) #000000 gray(0)
        47: (  0,  0,  0) #000000 gray(0)
        48: (  0,  0,  0) #000000 gray(0)
        49: (  0,  0,  0) #000000 gray(0)
        50: (  0,  0,  0) #000000 gray(0)
        51: (  0,  0,  0) #000000 gray(0)
        52: (  0,  0,  0) #000000 gray(0)
        53: (  0,  0,  0) #000000 gray(0)
        54: (  0,  0,  0) #000000 gray(0)
        55: (  0,  0,  0) #000000 gray(0)
        56: (  0,  0,  0) #000000 gray(0)
        57: (  0,  0,  0) #000000 gray(0)
        58: (  0,  0,  0) #000000 gray(0)
        59: (  0,  0,  0) #000000 gray(0)
        60: (  0,  0,  0) #000000 gray(0)
        61: (  0,  0,  0) #000000 gray(0)
        62: (  0,  0,  0) #000000 gray(0)
        63: (  0,  0,  0) #000000 gray(0)
        64: (  0,  0,  0) #000000 gray(0)
        65: (  0,  0,  0) #000000 gray(0)
        66: (  0,  0,  0) #000000 gray(0)
        67: (  0,  0,  0) #000000 gray(0)
        68: (  0,  0,  0) #000000 gray(0)
        69: (  0,  0,  0) #000000 gray(0)
        70: (  0,  0,  0) #000000 gray(0)
        71: (  0,  0,  0) #000000 gray(0)
        72: (  0,  0,  0) #000000 gray(0)
        73: (  0,  0,  0) #000000 gray(0)
        74: (  0,  0,  0) #000000 gray(0)
        75: (  0,  0,  0) #000000 gray(0)
        76: (  0,  0,  0) #000000 gray(0)
        77: (  0,  0,  0) #000000 gray(0)
        78: (  0,  0,  0) #000000 gray(0)
        79: (  0,  0,  0) #000000 gray(0)
        80: (  0,  0,  0) #000000 gray(0)
        81: (  0,  0,  0) #000000 gray(0)
        82: (  0,  0,  0) #000000 gray(0)
        83: (  0,  0,  0) #000000 gray(0)
        84: (  0,  0,  0) #000000 gray(0)
        85: (  0,  0,  0) #000000 gray(0)
        86: (  0,  0,  0) #000000 gray(0)
        87: (  0,  0,  0) #000000 gray(0)
        88: (  0,  0,  0) #000000 gray(0)
        89: (  0,  0,  0) #000000 gray(0)
        90: (  0,  0,  0) #000000 gray(0)
        91: (  0,  0,  0) #000000 gray(0)
        92: (  0,  0,  0) #000000 gray(0)
        93: (  0,  0,  0) #000000 gray(0)
        94: (  0,  0,  0) #000000 gray(0)
        95: (  0,  0,  0) #000000 gray(0)
        96: (  0,  0,  0) #000000 gray(0)
        97: (  0,  0,  0) #000000 gray(0)
        98: (  0,  0,  0) #000000 gray(0)
        99: (  0,  0,  0) #000000 gray(0)
       100: (  0,  0,  0) #000000 gray(0)
       101: (  0,  0,  0) #000000 gray(0)
       102: (  0,  0,  0) #000000 gray(0)
       103: (  0,  0,  0) #000000 gray(0)
       104: (  0,  0,  0) #000000 gray(0)
       105: (  0,  0,  0) #000000 gray(0)
       106: (  0,  0,  0) #000000 gray(0)
       107: (  0,  0,  0) #000000 gray(0)
       108: (  0,  0,  0) #000000 gray(0)
       109: (  0,  0,  0) #000000 gray(0)
       110: (  0,  0,  0) #000000 gray(0)
       111: (  0,  0,  0) #000000 gray(0)
       112: (  0,  0,  0) #000000 gray(0)
       113: (  0,  0,  0) #000000 gray(0)
       114: (  0,  0,  0) #000000 gray(0)
       115: (  0,  0,  0) #000000 gray(0)
       116: (  0,  0,  0) #000000 gray(0)
       117: (  0,  0,  0) #000000 gray(0)
       118: (  0,  0,  0) #000000 gray(0)
       119: (  0,  0,  0) #000000 gray(0)
       120: (  0,  0,  0) #000000 gray(0)
       121: (  0,  0,  0) #000000 gray(0)
       122: (  0,  0,  0) #000000 gray(0)
       123: (  0,  0,  0) #000000 gray(0)
       124: (  0,  0,  0) #000000 gray(0)
       125: (  0,  0,  0) #000000 gray(0)
       126: (  0,  0,  0) #000000 gray(0)
       127: (  0,  0,  0) #000000 gray(0)
       128: (  0,  0,  0) #000000 gray(0)
       129: (  0,  0,  0) #000000 gray(0)
       130: (  0,  0,  0) #000000 gray(0)
       131: (  0,  0,  0) #000000 gray(0)
       132: (  0,  0,  0) #000000 gray(0)
       133: (  0,  0,  0) #000000 gray(0)
       134: (  0,  0,  0) #000000 gray(0)
       135: (  0,  0,  0) #000000 gray(0)
       136: (  0,  0,  0) #000000 gray(0)
       137: (  0,  0,  0) #000000 gray(0)
       138: (  0,  0,  0) #000000 gray(0)
       139: (  0,  0,  0) #000000 gray(0)
       140: (  0,  0,  0) #000000 gray(0)
       141: (  0,  0,  0) #000000 gray(0)
       142: (  0,  0,  0) #000000 gray(0)
       143: (  0,  0,  0) #000000 gray(0)
       144: (  0,  0,  0) #000000 gray(0)
       145: (  0,  0,  0) #000000 gray(0)
       146: (  0,  0,  0) #000000 gray(0)
       147: (  0,  0,  0) #000000 gray(0)
       148: (  0,  0,  0) #000000 gray(0)
       149: (  0,  0,  0) #000000 gray(0)
       150: (  0,  0,  0) #000000 gray(0)
       151: (  0,  0,  0) #000000 gray(0)
       152: (  0,  0,  0) #000000 gray(0)
       153: (  0,  0,  0) #000000 gray(0)
       154: (  0,  0,  0) #000000 gray(0)
       155: (  0,  0,  0) #000000 gray(0)
       156: (  0,  0,  0) #000000 gray(0)
       157: (  0,  0,  0) #000000 gray(0)
       158: (  0,  0,  0) #000000 gray(0)
       159: (  0,  0,  0) #000000 gray(0)
       160: (  0,  0,  0) #000000 gray(0)
       161: (  0,  0,  0) #000000 gray(0)
       162: (  0,  0,  0) #000000 gray(0)
       163: (  0,  0,  0) #000000 gray(0)
       164: (  0,  0,  0) #000000 gray(0)
       165: (  0,  0,  0) #000000 gray(0)
       166: (  0,  0,  0) #000000 gray(0)
       167: (  0,  0,  0) #000000 gray(0)
       168: (  0,  0,  0) #000000 gray(0)
       169: (  0,  0,  0) #000000 gray(0)
       170: (  0,  0,  0) #000000 gray(0)
       171: (  0,  0,  0) #000000 gray(0)
       172: (  0,  0,  0) #000000 gray(0)
       173: (  0,  0,  0) #000000 gray(0)
       174: (  0,  0,  0) #000000 gray(0)
       175: (  0,  0,  0) #000000 gray(0)
       176: (  0,  0,  0) #000000 gray(0)
       177: (  0,  0,  0) #000000 gray(0)
       178: (  0,  0,  0) #000000 gray(0)
       179: (  0,  0,  0) #000000 gray(0)
       180: (  0,  0,  0) #000000 gray(0)
       181: (  0,  0,  0) #000000 gray(0)
       182: (  0,  0,  0) #000000 gray(0)
       183: (  0,  0,  0) #000000 gray(0)
       184: (  0,  0,  0) #000000 gray(0)
       185: (  0,  0,  0) #000000 gray(0)
       186: (  0,  0,  0) #000000 gray(0)
       187: (  0,  0,  0) #000000 gray(0)
       188: (  0,  0,  0) #000000 gray(0)
       189: (  0,  0,  0) #000000 gray(0)
       190: (  0,  0,  0) #000000 gray(0)
       191: (  0,  0,  0) #000000 gray(0)
       192: (  0,  0,  0) #000000 gray(0)
       193: (  0,  0,  0) #000000 gray(0)
       194: (  0,  0,  0) #000000 gray(0)
       195: (  0,  0,  0) #000000 gray(0)
       196: (  0,  0,  0) #000000 gray(0)
       197: (  0,  0,  0) #000000 gray(0)
       198: (  0,  0,  0) #000000 gray(0)
       199: (  0,  0,  0) #000000 gray(0)
       200: (  0,  0,  0) #000000 gray(0)
       201: (  0,  0,  0) #000000 gray(0)
       202: (  0,  0,  0) #000000 gray(0)
       203: (  0,  0,  0) #000000 gray(0)
       204: (  0,  0,  0) #000000 gray(0)
       205: (  0,  0,  0) #000000 gray(0)
       206: (  0,  0,  0) #000000 gray(0)
       207: (  0,  0,  0) #000000 gray(0)
       208: (  0,  0,  0) #000000 gray(0)
       209: (  0,  0,  0) #000000 gray(0)
       210: (  0,  0,  0) #000000 gray(0)
       211: (  0,  0,  0) #000000 gray(0)
       212: (  0,  0,  0) #000000 gray(0)
       213: (  0,  0,  0) #000000 gray(0)
       214: (  0,  0,  0) #000000 gray(0)
       215: (  0,  0,  0) #000000 gray(0)
       216: (  0,  0,  0) #000000 gray(0)
       217: (  0,  0,  0) #000000 gray(0)
       218: (  0,  0,  0) #000000 gray(0)
       219: (  0,  0,  0) #000000 gray(0)
       220: (  0,  0,  0) #000000 gray(0)
       221: (  0,  0,  0) #000000 gray(0)
       222: (  0,  0,  0) #000000 gray(0)
       223: (  0,  0,  0) #000000 gray(0)
       224: (  0,  0,  0) #000000 gray(0)
       225: (  0,  0,  0) #000000 gray(0)
       226: (  0,  0,  0) #000000 gray(0)
       227: (  0,  0,  0) #000000 gray(0)
       228: (  0,  0,  0) #000000 gray(0)
       229: (  0,  0,  0) #000000 gray(0)
       230: (  0,  0,  0) #000000 gray(0)
       231: (  0,  0,  0) #000000 gray(0)
       232: (  0,  0,  0) #000000 gray(0)
       233: (  0,  0,  0) #000000 gray(0)
       234: (  0,  0,  0) #000000 gray(0)
       235: (  0,  0,  0) #000000 gray(0)
       236: (  0,  0,  0) #000000 gray(0)
       237: (  0,  0,  0) #000000 gray(0)
       238: (  0,  0,  0) #000000 gray(0)
       239: (  0,  0,  0) #000000 gray(0)
       240: (  0,  0,  0) #000000 gray(0)
       241: (  0,  0,  0) #000000 gray(0)
       242: (  0,  0,  0) #000000 gray(0)
       243: (  0,  0,  0) #000000 gray(0)
       244: (  0,  0,  0) #000000 gray(0)
       245: (  0,  0,  0) #000000 gray(0)
       246: (  0,  0,  0) #000000 gray(0)
       247: (  0,  0,  0) #000000 gray(0)
       248: (192,192,192) #C0C0C0 gray(192)
       249: (255,  0,  0) #FF0000 gray(255)
       250: (  0,255,  0) #00FF00 gray(0)
       251: (255,255,  0) #FFFF00 gray(255)
       252: (  0,  0,255) #0000FF gray(0)
       253: (255,  0,255) #FF00FF gray(255)
       254: (  0,255,255) #00FFFF gray(0)
       255: (255,255,255) #FFFFFF gray(255)
  Rendering intent: Perceptual
  Gamma: 0.454545
  Chromaticity:
    red primary: (0.64,0.33)
    green primary: (0.3,0.6)
    blue primary: (0.15,0.06)
    white point: (0.3127,0.329)
  Background color: gray(255)
  Border color: gray(223)
  Matte color: gray(189)
  Transparent color: gray(0)
  Interlace: None
  Intensity: Undefined
  Compose: Over
  Page geometry: 512x512+0+0
  Dispose: Undefined
  Iterations: 0
  Compression: Undefined
  Orientation: Undefined
  Properties:
    date:create: 2014-10-01T09:18:15+01:00
    date:modify: 2002-11-25T01:33:53+00:00
    signature: dcd0e6587dcdeaaba5999a9bb384473f1af19f7a4c09ffee95356ea51bec22ce
  Artifacts:
    filename: /Users/mark/Desktop/lena.bmp
    verbose: true
  Tainted: True
  Filesize: 263KB
  Number pixels: 262K
  Pixels per second: 26.21MB
  User time: 0.000u
  Elapsed time: 0:01.009
  Version: ImageMagick 6.8.9-7 Q16 x86_64 2014-09-10 http://www.imagemagick.org

如您所见，图像中只有 28 种独特的颜色，并且调色板只是部分填充，正如您所指出的。

另一种可以帮助您调试代码的技术是让 ImageMagick 将整个图像转储为文本，如下所示 - 我只显示前 8 个像素，但您明白了：

convert lena.bmp -colorspace rgb txt:- | more

# ImageMagick pixel enumeration: 512,512,255,rgb
0,0: (85,85,85)  #555555  rgb(85,85,85)
1,0: (95,95,95)  #5F5F5F  rgb(95,95,95)
2,0: (85,85,85)  #555555  rgb(85,85,85)
3,0: (95,95,95)  #5F5F5F  rgb(95,95,95)
4,0: (95,95,95)  #5F5F5F  rgb(95,95,95)
5,0: (85,85,85)  #555555  rgb(85,85,85)
6,0: (95,95,95)  #5F5F5F  rgb(95,95,95)
7,0: (85,85,85)  #555555  rgb(85,85,85)

【讨论】：

猜你喜欢
  • 2011-05-03
  • 1970-01-01
  • 1970-01-01
  • 1970-01-01
  • 1970-01-01
  • 2021-09-12
  • 1970-01-01
  • 1970-01-01
相关资源
最近更新 更多
热门标签
Java Python linux javascript Mysql C# Docker 算法 前端 SpringBoot Redis Vue spring 设计模式 .net core .net kubernetes c++ 数据库 数据结构 大数据 js 机器学习 微服务 Android Go 程序员 面试 JVM ASP.net core 云原生 人工智能 后端 PHP git CSS golang k8s Nginx Django mybatis 深度学习 多线程 React 架构 devops 爬虫 云计算 Spring Boot LeetCode