Error Object Reference not set to an instance of an Object

Asked

Viewed 788 times

1

I can’t find the error of this code when saving the webcam image, whenever I click save as and type the file name it returns me with this error

using System;
using System.Drawing;
using System.Windows.Forms;

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {

        public DirectX.Capture.Filter Camera;
        public DirectX.Capture.Capture CaptureInfo;
        public DirectX.Capture.Filters CamContainer;
        Image capturaImagem;
        public string caminhoImagemSalva = null ;

        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
           CamContainer = new DirectX.Capture.Filters();  
           try
           {
             int no_of_cam = CamContainer.VideoInputDevices.Count;
#pragma warning disable CS0162 // Unreachable code detected
                for (int i = 0; i < no_of_cam; i++)
#pragma warning restore CS0162 // Unreachable code detected
                {
                try
                {
                        // obtém o dispositivo de entrada do vídeo
                        Camera = CamContainer.VideoInputDevices[i];

                        // inicializa a Captura usando o dispositivo
                        CaptureInfo = new DirectX.Capture.Capture(Camera, null);

                        // Define a janela de visualização do vídeo
                        CaptureInfo.PreviewWindow = this.picWebCam;

                        // Capturando o tratamento de evento
                        CaptureInfo.FrameCaptureComplete += AtualizaImagem;

                        // Captura o frame do dispositivo
                        CaptureInfo.CaptureFrame();

                        // Se o dispositivo foi encontrado e inicializado então sai sem checar o resto
                        break;
                }
                catch (Exception ex) 
                {
                    throw ex;    
                }
            }

                {
                    this.TopMost = false;
                    this.FormBorderStyle = FormBorderStyle.None;
                    this.WindowState = FormWindowState.Maximized;
                }
            }
        catch (Exception ex)
        {                
            MessageBox.Show(this, ex.Message);
        }
     }

        public void AtualizaImagem(PictureBox frame)
        {
            try
            {
                capturaImagem = frame.Image;
                this.picImagem.Image = capturaImagem;
            }
            catch (Exception ex)
            {
                MessageBox.Show("Erro " + ex.Message);
            }
        }

        private void btnCaptura_Click(object sender, EventArgs e)
        {
            try
            {
                CaptureInfo.CaptureFrame();
            }
            catch (Exception ex)
            {
                MessageBox.Show("Erro " + ex.Message);
            }
        }

        private void btnSalvar_Click(object sender, System.EventArgs e)
        {
            try
            {
                //abre a opção de salvar como, para selecionar a pasta
                SaveFileDialog saveFileDialog1 = new SaveFileDialog
            {
                Filter = "JPeg Image|*.jpg|Bitmap Image|*.bmp|Gif Image|*.gif",
                Title = "Salvar o arquivo de imagem",
                InitialDirectory = @"C:\Users\ssbfci\Documents\FOTOS DO FERRAMENTAL\"
            };
            saveFileDialog1.ShowDialog();

                // se o nome do arquivo não for vazio, abre para salvar
                if (saveFileDialog1.FileName != "")
                {
                    // salva a imagem por fileStream
                    System.IO.FileStream fs =
                       (System.IO.FileStream)saveFileDialog1.OpenFile();
                    // Salva a imagem no formato certo
                    switch (saveFileDialog1.FilterIndex)
                    {
                        case 1:
                            this.btnSalvar.Image.Save(fs,
                               System.Drawing.Imaging.ImageFormat.Jpeg);
                            break;

                        case 2:
                            this.btnSalvar.Image.Save(fs,
                               System.Drawing.Imaging.ImageFormat.Bmp);
                            break;

                        case 3:
                            this.btnSalvar.Image.Save(fs,
                               System.Drawing.Imaging.ImageFormat.Gif);
                            break;
                    }

                    fs.Close();
                }

            }
            catch (Exception ex)
            {
                MessageBox.Show("Erro " + ex.Message);
            }
        }

        private void pictureBox1_Click(object sender, EventArgs e)
        {

        }
    }
}

Designer

namespace WindowsFormsApplication1
{
    partial class Form1
    {
        /// <summary>
        /// Required designer variable.
        /// </summary>
        private System.ComponentModel.IContainer components = null;

        /// <summary>
        /// Clean up any resources being used.
        /// </summary>
        /// <param name="disposing">true if managed resources should be disposed; otherwise, false.</param>
        protected override void Dispose(bool disposing)
        {
            if (disposing && (components != null))
            {
                components.Dispose();
            }
            base.Dispose(disposing);
        }

        #region Windows Form Designer generated code

        /// <summary>
        /// Required method for Designer support - do not modify
        /// the contents of this method with the code editor.
        /// </summary>
        private void InitializeComponent()
        {
            System.ComponentModel.ComponentResourceManager resources = new System.ComponentModel.ComponentResourceManager(typeof(Form1));
            this.picWebCam = new System.Windows.Forms.PictureBox();
            this.picImagem = new System.Windows.Forms.PictureBox();
            this.btnCaptura = new System.Windows.Forms.Button();
            this.btnSalvar = new System.Windows.Forms.Button();
            this.pictureBox1 = new System.Windows.Forms.PictureBox();
            this.textBox1 = new System.Windows.Forms.TextBox();
            ((System.ComponentModel.ISupportInitialize)(this.picWebCam)).BeginInit();
            ((System.ComponentModel.ISupportInitialize)(this.picImagem)).BeginInit();
            ((System.ComponentModel.ISupportInitialize)(this.pictureBox1)).BeginInit();
            this.SuspendLayout();
            // 
            // picWebCam
            // 
            this.picWebCam.BackColor = System.Drawing.Color.White;
            this.picWebCam.BorderStyle = System.Windows.Forms.BorderStyle.Fixed3D;
            this.picWebCam.Location = new System.Drawing.Point(172, 133);
            this.picWebCam.Margin = new System.Windows.Forms.Padding(4);
            this.picWebCam.Name = "picWebCam";
            this.picWebCam.Size = new System.Drawing.Size(715, 503);
            this.picWebCam.TabIndex = 0;
            this.picWebCam.TabStop = false;
            // 
            // picImagem
            // 
            this.picImagem.BorderStyle = System.Windows.Forms.BorderStyle.FixedSingle;
            this.picImagem.Location = new System.Drawing.Point(1021, 133);
            this.picImagem.Margin = new System.Windows.Forms.Padding(4);
            this.picImagem.Name = "picImagem";
            this.picImagem.Size = new System.Drawing.Size(697, 503);
            this.picImagem.SizeMode = System.Windows.Forms.PictureBoxSizeMode.StretchImage;
            this.picImagem.TabIndex = 1;
            this.picImagem.TabStop = false;
            // 
            // btnCaptura
            // 
            this.btnCaptura.Font = new System.Drawing.Font("Microsoft Sans Serif", 14.25F, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, ((byte)(0)));
            this.btnCaptura.Location = new System.Drawing.Point(237, 668);
            this.btnCaptura.Margin = new System.Windows.Forms.Padding(4);
            this.btnCaptura.Name = "btnCaptura";
            this.btnCaptura.Size = new System.Drawing.Size(581, 55);
            this.btnCaptura.TabIndex = 2;
            this.btnCaptura.Text = "Capturar Imagem";
            this.btnCaptura.UseVisualStyleBackColor = true;
            this.btnCaptura.Click += new System.EventHandler(this.btnCaptura_Click);
            // 
            // btnSalvar
            // 
            this.btnSalvar.Click += new System.EventHandler(this.btnSalvar_Click);
            this.btnSalvar.Font = new System.Drawing.Font("Microsoft Sans Serif", 14.25F, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, ((byte)(0)));
            this.btnSalvar.Location = new System.Drawing.Point(1080, 668);
            this.btnSalvar.Margin = new System.Windows.Forms.Padding(4);
            this.btnSalvar.Name = "btnSalvar";
            this.btnSalvar.Size = new System.Drawing.Size(581, 55);
            this.btnSalvar.TabIndex = 3;
            this.btnSalvar.Text = "Salvar Imagem";
            this.btnSalvar.UseVisualStyleBackColor = true;

            // 
            // pictureBox1
            // 
            this.pictureBox1.Image = ((System.Drawing.Image)(resources.GetObject("pictureBox1.Image")));
            this.pictureBox1.Location = new System.Drawing.Point(378, 730);
            this.pictureBox1.Name = "pictureBox1";
            this.pictureBox1.Size = new System.Drawing.Size(1065, 310);
            this.pictureBox1.TabIndex = 4;
            this.pictureBox1.TabStop = false;
            // 
            // textBox1
            // 
            this.textBox1.BackColor = System.Drawing.SystemColors.ActiveCaption;
            this.textBox1.BorderStyle = System.Windows.Forms.BorderStyle.None;
            this.textBox1.Font = new System.Drawing.Font("Times New Roman", 48F, System.Drawing.FontStyle.Bold, System.Drawing.GraphicsUnit.Point, ((byte)(0)));
            this.textBox1.ForeColor = System.Drawing.Color.Red;
            this.textBox1.Location = new System.Drawing.Point(515, 29);
            this.textBox1.Name = "textBox1";
            this.textBox1.Size = new System.Drawing.Size(893, 74);
            this.textBox1.TabIndex = 5;
            this.textBox1.Text = "CAIXA DE PEÇA SEPARADA";
            // 
            // Form1
            // 
            this.AutoScaleDimensions = new System.Drawing.SizeF(8F, 16F);
            this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
            this.BackColor = System.Drawing.SystemColors.ActiveCaption;
            this.ClientSize = new System.Drawing.Size(1864, 1062);
            this.Controls.Add(this.textBox1);
            this.Controls.Add(this.pictureBox1);
            this.Controls.Add(this.btnSalvar);
            this.Controls.Add(this.btnCaptura);
            this.Controls.Add(this.picImagem);
            this.Controls.Add(this.picWebCam);
            this.Font = new System.Drawing.Font("Microsoft Sans Serif", 9.75F, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, ((byte)(0)));
            this.Margin = new System.Windows.Forms.Padding(4);
            this.Name = "Form1";
            this.StartPosition = System.Windows.Forms.FormStartPosition.CenterScreen;
            this.Text = "Capturando Imagem da WebCam";
            this.Load += new System.EventHandler(this.Form1_Load);
            ((System.ComponentModel.ISupportInitialize)(this.picWebCam)).EndInit();
            ((System.ComponentModel.ISupportInitialize)(this.picImagem)).EndInit();
            ((System.ComponentModel.ISupportInitialize)(this.pictureBox1)).EndInit();
            this.ResumeLayout(false);
            this.PerformLayout();

        }

        #endregion

        private System.Windows.Forms.PictureBox picWebCam;
        private System.Windows.Forms.PictureBox picImagem;
        private System.Windows.Forms.Button btnCaptura;
        private System.Windows.Forms.Button btnSalvar;
        private System.Windows.Forms.PictureBox pictureBox1;
        private System.Windows.Forms.TextBox textBox1;
    }
}
c#

  • it is likely that fs is void. Take the Try catch to see the bug or break point the catch and see the stacktrace.

  • I did what you said, he returns to me like this System.NullReferenceException: 'Object reference not set to an instance of an object.'&#xA;System.Windows.Forms.ButtonBase.Image.get returned null.

1 answer

7


You are trying to save the image from the button btnSalvar instead of the image captured by the webcam.

change:

this.btnSalvar.Image.Save(fs,System.Drawing.Imaging.ImageFormat.Jpeg);

for

this.picImagem.Image.Save(fs,System.Drawing.Imaging.ImageFormat.Jpeg);

on all lines inside the switch.

Before the switch, check whether this.picImagem.Image is void before continuing.

  • 1

    Thank you so much, now it’s been right

  • 1

    Another important detail: it is important to close the file (fs.close()) in instruction catch. Otherwise, you will not be able to save over the same file when error occurs because it will get allocated for another process.

  • good @Fernando, thanks for the tip

Browser other questions tagged c#

You are not signed in. Login or sign up in order to post.