C#合并BitMap图像生成超大bitmap
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2022-06-15 18:42:14
当只需要两个图像合并的时候,可以简单的使用gdi+,把两个图像画到一个画布上面实现合并bitmap.当需要将许多bitmap合并时,由于bitmap类限制,长度或宽度太大时会报异常,前面这种方法就行不...
当只需要两个图像合并的时候,可以简单的使用gdi+,把两个图像画到一个画布上面实现合并bitmap.
当需要将许多bitmap合并时,由于bitmap类限制,长度或宽度太大时会报异常,前面这种方法就行不通了。
由于bitmapp属于位图格式,了解图像格式后,发现,bitmap文件的第3-8位存储了文件大小信息,第19-22位存储了高度信息,第23-26位存储了宽度信息。文件头后面都是像素的argb,并无其它信息。于是,试想一下,如果把第二张图像的像素argb放到第一张后面,并修改第一张的文件头信息,是不是就可以实现文件合并了呢。事实证明:yes。
//设置文件头里面文件大小信息 public void setbitmapfilesizeinfo(string filepath) { fileinfo fileinfo = new fileinfo(filepath); long le = fileinfo.length; string hexsize = le.tostring("x").padleft(8, '0'); int size1 = convert.toint32(hexsize.substring(0, 2), 16); int size2 = convert.toint32(hexsize.substring(2, 2), 16); int size3 = convert.toint32(hexsize.substring(4, 2), 16); int size4 = convert.toint32(hexsize.substring(6, 2), 16); byte[] sizebytes = new byte[] { (byte)size4, (byte)size3, (byte)size2, (byte)size1 }; using (filestream fs = new filestream(filepath, filemode.open, fileaccess.write)) { using (binarywriter r = new binarywriter(fs)) { r.seek(2, 0); r.write(sizebytes, 0, sizebytes.length); } } }
设置文件头里面文件长度和宽度信息
public void setbitmapsizeinfo(string filepath,int width=0,int height=0) { if (height != 0) { string hexheight = height.tostring("x").padleft(8, '0'); int h1 = convert.toint32(hexheight.substring(0, 2), 16); int h2 = convert.toint32(hexheight.substring(2, 2), 16); int h3 = convert.toint32(hexheight.substring(4, 2), 16); int h4 = convert.toint32(hexheight.substring(6, 2), 16); byte[] sizeheight = new byte[] { (byte)h4, (byte)h3, (byte)h2, (byte)h1 }; using (filestream fs = new filestream(filepath, filemode.open, fileaccess.readwrite)) { using (binarywriter r = new binarywriter(fs)) { r.seek(22, 0);//高度保存位置 r.write(sizeheight, 0, sizeheight.length); } } } if (width != 0) { string hexwidth = height.tostring("x").padleft(8, '0'); int w1 = convert.toint32(hexwidth.substring(0, 2), 16); int w2 = convert.toint32(hexwidth.substring(2, 2), 16); int w3 = convert.toint32(hexwidth.substring(4, 2), 16); int w4 = convert.toint32(hexwidth.substring(6, 2), 16); byte[] sizewidth = new byte[] { (byte)w4, (byte)w3, (byte)w2, (byte)w1 }; using (filestream fs = new filestream(filepath, filemode.open, fileaccess.readwrite)) { using (binarywriter r = new binarywriter(fs)) { r.seek(18, 0);//高度保存位置 r.write(sizewidth, 0, sizewidth.length); } } } }
合并多个bitmap文件,并生成一个最终文件
private void createbitmap(string temppath,string imagepath) { string[] files = directory.getfiles(temppath, "*.png"); bitmap bmp; int height=0; for (int i = files.length-1; i >0; i--) { string filename = files[i]; bmp = new bitmap(filename); if (i == files.length - 1) { bmp.save(imagepath, imageformat.bmp); height += bmp.height; bmp.dispose(); continue; } else { byte[] bytes = getimagerasterbytes(bmp, pixelformat.format32bpprgb); using (filestream fs = new filestream(imagepath, filemode.open, fileaccess.write)) { fs.seek(fs.length, 0); fs.write(bytes, 0, bytes.length); } height += bmp.height; bmp.dispose(); } } setbitmapfilesizeinfo(imagepath); setbitmapsizeinfo(imagepath, height: height); //messagebox.show("合并成功"); } private static byte[] getimagerasterbytes(bitmap bmp, pixelformat format) { rectangle rect = new rectangle(0, 0, bmp.width, bmp.height); byte[] bits = null; try { // lock the managed memory bitmapdata bmpdata = bmp.lockbits(rect, imagelockmode.readwrite, format); // declare an array to hold the bytes of the bitmap. bits = new byte[bmpdata.stride * bmpdata.height]; // copy the values into the array. system.runtime.interopservices.marshal.copy(bmpdata.scan0, bits, 0, bits.length); // release managed memory bmp.unlockbits(bmpdata); } catch { return null; } return bits; }
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