从位图图像中提取RGB值

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你好。我目前正在尝试从256色位图图像中提取R，G，B值（用于测试目的，固定宽度为152，高度为150）。我已经使用BITMAPINFOHEADER和BITMAPFILEHEADER检查了偏移量为1078，每像素字节数为1. 图像数据最初放入二维数组中，然后放入一维数组。分配了三个2维数组来保存每个像素的R，G，B值。 当我运行程序时，以下的Debug Assertion失败了！消息出现： 表达式：_BLOCK_TYPE_IS_VALID（pHead-> nBlockUse） 以下是代码，我会重视您的专家反馈以及如何修复此错误。

Hello. I am currently trying to extract R, G, B values from a 256 colour bitmap image (using for testing purposes a fixed width of 152 and height 150). I have checked using BITMAPINFOHEADER and BITMAPFILEHEADER that the offset is 1078 and bytes per pixel is 1. The image data is initially placed in a 2 dimensional array before being placed into a 1 dimensional array. Three 2 dimensional arrays were allocated to hold the R, G, B values from each pixel. When I run the program, the following Debug Assertion Failed! message appears: Expression: _BLOCK_TYPE_IS_VALID (pHead->nBlockUse) Below is the code and I would value your expert feedback and how to fix this error.

unsigned char** Allocate2DArray(unsigned char** buffer, int w, int h) { buffer = new unsigned char*[h]; if(buffer == NULL) return 0; // return if memory not allocated // For each of these pointers, allocate memory of size ‘w’ for(int j=0; j<h; j++) { buffer[j] = new unsigned char[w]; if(buffer[j] == NULL) return 0;// return if not allocated } return buffer; } void DeAllocate2DArray(unsigned char** buffer, int h) { // After complete usage, delete the memory dynamically allocated for(int j=h-1; j>= 0; j--) delete[] buffer[j]; //delete rows delete[] buffer; //delete the pointer to pointer } using namespace std; int main() { ifstream image; image.open("image.bmp",std::ios_base::binary); if (image.is_open()) { cout<< "function success\n"; } else { cout<< "unable to open file"; } const int width = 152; const int height = 150; unsigned char m_cHeaderData[1078]; unsigned char** m_cImageData = new unsigned char* [height]; for( int i = 0; i <height; i++) { m_cImageData[i] = new unsigned char [width]; } ifstream* m_pInFile; m_pInFile = new ifstream; m_pInFile->open("image.bmp", ios::in | ios::binary); m_pInFile->seekg(0, ios::beg); m_pInFile->read(reinterpret_cast<char*>(m_cHeaderData), 1078); //bitmap bits start at offset 1078 for(int i = 0; i <height; i++) { m_pInFile->read(reinterpret_cast<char*>(m_cImageData[i]), width); } m_pInFile->close(); // Declare a pointer of the type you want. // This will point to the 1D array unsigned char* array_1D; // Now allocate memory for array_1D array_1D = new unsigned char[height*width]; if(array_1D == NULL) return 0; // return if memory not allocated // Copy contents from the existing 2D array int offset = 0; for(int j=0; j<height; j++) // traverse height (or rows) { offset = width * j; for(int i=0; i<width; i++) // traverse width { array_1D[offset + i] = m_cImageData[j][i]; // update value at current (i, j) } } // Declare three 2D arrays to store R,G, and B planes of image. unsigned char**arrayR_2D, **arrayG_2D, **arrayB_2D; arrayR_2D = Allocate2DArray(arrayR_2D, width, height); arrayG_2D = Allocate2DArray(arrayG_2D, width, height); arrayB_2D = Allocate2DArray(arrayB_2D, width, height); // return if memory not allocated if(arrayR_2D == NULL || arrayG_2D == NULL || arrayB_2D == NULL) return 0; // Extract R,G,B planes from the existing composite 1D array int offsetx = 0; int counter = 0; int bytesPerPixel = 1; for(int j=0; j<height; j++) // traverse height (or rows) { offset = width * j; for(int i=0; i<width*bytesPerPixel; i+=bytesPerPixel) // width { arrayB_2D[j][counter++] = array_1D[offsetx + i+0]; arrayG_2D[j][counter++] = array_1D[offsetx + i+1]; arrayR_2D[j][counter++] = array_1D[offsetx + i+2]; } counter = 0; } // After complete usage, delete the memory dynamically allocated DeAllocate2DArray(arrayR_2D, height); DeAllocate2DArray(arrayG_2D, height); DeAllocate2DArray(arrayB_2D, height); // After complete usage, delete the memory dynamically allocated delete[] array_1D; //delete the pointer to pointer //deallocate memory: delete m_pInFile; delete m_pOutFile; for(int i = 0; i <height; i++) { delete[] m_cImageData[i]; } delete[] m_cImageData; system("pause"); return 0; }

推荐答案

错误在于： The error is here: //deallocate memory: delete m_pInFile; delete m_pOutFile;

m_pInFile 和 m_pInFile 是流而不是内存指针。 正确答案应该是： 这些对象尚未使用 new 在堆上分配，但是位于堆栈上，因此无法销毁使用删除。

m_pInFile and m_pInFile are streams and not memory pointers. The correct answer should be: These objects have not been allocated on the heap using new but are located on the stack and can't be therefore destroyed using delete.