C++ 从数字数组创建 png/位图

问题描述

所以我找到了关于我的问题的链接，但它是针对 c# 的

用于转换和放大的 ImageMagick 命令是这样的:

convert image.ppm -scale 400x result.png

如果 ImageMagick 有点重量级，或者难以安装，您可以更简单地使用 NetPBM 工具(来自 此处) 像这样(它是一个单独的预编译二进制文件)

pnmtopng image.ppm >结果.png

So i found this link regarding my question, but it is for c#

Create a PNG from an array of bytes

I have a variable int array of numbers.i will call it "pix[ ]"for now it can be any size from 3 to 256, later possibly bigger.

What i want to do now, is to convert it into a pixel image.I am still a noobin c++ so pleas excuse me.I tried to download some libaries that make working with libpng easier, but they do not seem to be working (ubuntu, code::blocks)So i have questions in the following:

1) how do you create a new bitmap (which libaries, which command)?

2) how do i fill it with information from "pix[ ]" ?

3) how do i save it?

if it is a repost of a question i am happy about a link also ;)

Here is what i worked out so far, thanks for your help.

int main(){
 FILE *imageFile;
 int x,y,pixel,height=2,width=3;

 imageFile=fopen("image.pgm","wb");
 if(imageFile==NULL){
  perror("ERROR: Cannot open output file");
  exit(EXIT_FAILURE);
 }

 fprintf(imageFile,"P3\n");           // P3 filetype
 fprintf(imageFile,"%d %d\n",width,height);   // dimensions
 fprintf(imageFile,"255\n");          // Max pixel
  int pix[100] {200,200,200, 100,100,100, 0,0,0, 255,0,0, 0,255,0, 0,0,255};


       fwrite(pix,1,18,imageFile);


fclose(imageFile);
}

i have not fully understood what it does. i can open the output image, but it is not a correct representation of the Array.

If i change things around, for example making a 2 dimensional array, then the image viewer tells me "expected an integer" and doesn't show me an image.

So far so good.As i have the array before the image i created a function aufrunden to round up to the next int number because i want to create a square image.

int aufrunden (double h)
{
int i =h;
if (h-i == 0)
  {
  return i;
  }
else
  {
  i = h+1;
  return i;
  }
}

This function is used in the creation of the image.If the image is bigger than the information the array provides like this (a is the length of th array)

double h;
h= sqrt(a/3.0);
int i = aufrunden(h);
FILE *imageFile;
int height=i,width=i;

It might happen now, that the array is a=24 long. aufrunden makes the image 3x3 so it has 27 values...meaning it is missing the values for 1 pixel.Or worse it is only a=23 long. also creating a 3x3 image.

What will fwrite(pix,1,18,imageFile); write in those pixels for information? It would be best if the remaing values are just 0.

*edit never mind, i will just add 0 to the end of the array until it is filling up the whole square...sorry

解决方案

Consider using a Netpbm format (pbm, pgm, or ppm).

These images are extremely simple text files that you can write without any special libraries. Then use some third-party software such as ImageMagick, GraphicsMagick, or pnmtopng to convert your image to PNG format. Here is a wiki article describing the Netpbm format.

Here's a simple PPM image:

P3 2 3 255
0 0 0       255 255 255
255 0 0     0 255 255
100 100 100 200 200 200

The first line contains "P3" (the "magic number identifying it as a text-PPM), 2 (width), 3 (height), 255 (maximum intensity).The second line contains the two RGB pixels for the top row.The third and fourth lines each contain the two RGB pixels for rows 2 and 3.

Use a larger number for maximum intensity (e.g. 1024) if you need a larger range of intensities, up to 65535.

Edited by Mark Setchell beyond this point - so I am the guilty party!

The image looks like this (when the six pixels are enlarged):

The ImageMagick command to convert, and enlarge, is like this:

convert image.ppm -scale 400x result.png

If ImageMagick is a bit heavyweight, or difficult to install you can more simply use the NetPBM tools (from here) like this (it's a single precompiled binary)

pnmtopng image.ppm > result.png

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