I need to shrink multiple images that contain text. Because of the text they need to be shrunk in such a way as to retain the sharp edges of the text and not smoothed. My first attempt was the following:
RenderOptions.SetBitmapScalingMode(upgradeCard, BitmapScalingMode.HighQuality);
upgradeCard.Height(resizedHeight);
upgradeCard.Width(resizedWidth);
The result was too blurry, the text was hard to read. It was, however, really really fast. I then tried this:
public static class ImageResizer
{
public static Image Resize(Image image, Size size)
{
if (image == null || size.IsEmpty)
return null;
var resizedImage = new Bitmap(size.Width, size.Height, image.PixelFormat);
resizedImage.SetResolution(image.HorizontalResolution, image.VerticalResolution);
using (var graphics = Graphics.FromImage(resizedImage))
{
var location = new Point(0, 0);
graphics.CompositingMode = CompositingMode.SourceCopy;
graphics.CompositingQuality = CompositingQuality.HighQuality;
graphics.InterpolationMode = InterpolationMode.HighQualityBicubic;
graphics.SmoothingMode = SmoothingMode.None;
graphics.DrawImage(image, new Rectangle(location, size),
new Rectangle(location, image.Size), GraphicsUnit.Pixel);
}
return resizedImage;
}
}
This worked really well, almost as good as Photoshop Bicubic Sharper. Unfortunately it was also very slow. Way too slow for what I need.
Is there any other way of doing this that produces the results of the second method but does so fairly quickly?
Without examples of your images it's hard to give reliable advice.
For example, how much contrast is in your images already? By what factor are you reducing them?
You could try nearest neighbour scaling, which can be very fast, and then try blurring the output slightly with a Gaussian filter, or similar. If that's too aliased, you could also try linear scaling with a soft blur.
Related
What I'm trying to do:
Since in my bitmaps there are some unwanted white edges around the picture that result from anti-aliasing as pointed out from another user from stackoverflow.
I'm trying to convert an image that's inputted into a bitmap, convert bitmap into a Graphics object so that I can set the Smooth Mode to none, and then finally convert that Graphics object to a bitmap so that it can be copied by the user after setting it to the clipboard. I'm not sure if this is a good way of getting rid anti-aliasing in bitmaps but I'm definitely interested in improvements and suggestions.
The issue I'm facing:
The result of the image after is completely blank and does not contain any of the pixels that are previously found in the original bitmap. Here's the result:
This issue applies to all pictures no matter what their format is.
My code:
public PicGen(PictureBox pictureBox)
{
Clipboard.Clear();
Bitmap firstImage = new(pictureBox.Image, pictureBox.Width, pictureBox.Height);
RectangleF cloneRect = new RectangleF(0, 0, firstImage.Width, firstImage.Height);
System.Drawing.Imaging.PixelFormat format = firstImage.PixelFormat;
Bitmap cloneBitmap = firstImage.Clone(cloneRect, format);
Graphics AntiARemover = Graphics.FromImage(cloneBitmap);
AntiARemover.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.None;
Bitmap finalImg = new(52, 52, AntiARemover);
Clipboard.SetImage(finalImg);
Color backColorBottom = firstImage.GetPixel(0, 0);
firstImage.ReplaceColor(backColorBottom, Color.FromArgb(54, 57, 63));
Bitmap finalImg = new(52, 52, AntiARemover);
From the documentation for this bitmap constructor:
The new Bitmap that this method creates takes its horizontal and vertical resolution from the DpiX and DpiY properties of g, respectively.
If you want create a new image with the content from another you need to call one of the DrawImage methods. You should also dispose your graphics object, and any temporary bitmaps you may use.
using var finalImg = new Bitmap(52,52);
using var graphics = Graphics.FromImage(finalImg);
graphics.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.None;
graphics.DrawImage(cloneBitmap)
However, edge artifacts typically occur when combining two images using an alpha channel, see Premultiplied alpha. In your example I can only see one input image, so I'm really not sure what it is you are actually trying to do. If you need to convert to premultiplied alpha you can use the following code to convert the color for each pixel
premultiplied.R = (byte)(straight.R * straight.A / 255);
premultiplied.G = (byte)(straight.G * straight.A / 255);
premultiplied.B = (byte)(straight.B * straight.A / 255);
premultiplied.A = straight.A;
Today I started using Tesseract to parse portions of my screen for numbers. I have had a decent amount of success with larger text (which results in a higher resolution image). Now I am trying to use Tesseract in a more practical sense and the image quality is too low. I have tried increasing the resolution and redrawing with anti-aliasing, but I am not sure if I am even doing these things right. Do you have any suggestions as to how I might be able to get Tesseract to recognize the "12" in my tiny image?
Image:
static public void test()
{
string readIn;
TesseractEngine engine = new TesseractEngine(#".\tessdata","eng", EngineMode.Default);
engine.SetVariable("tessedit_char_whitelist", "0123456789"); //only read as numbers
Rectangle rect = new Rectangle(181, 107, 25, 25);
Bitmap bmp = new Bitmap(rect.Width, rect.Height, PixelFormat.Format32bppArgb);
Graphics g = Graphics.FromImage(bmp);
g.CopyFromScreen(rect.Left, rect.Top, 0, 0, bmp.Size, CopyPixelOperation.SourceCopy);
g.InterpolationMode = InterpolationMode.High;
g.CompositingQuality = CompositingQuality.HighQuality;
g.SmoothingMode = SmoothingMode.AntiAlias;
g.DrawImage(bmp, rect.Width, rect.Height); //Do some anti-aliasing hopefully?
bmp.SetResolution(300, 300) //Try increasing resolution??
bmp.Save(#".\tmp.jpg");
readIn = engine.Process(PixConverter.ToPix(bmp)).GetText();
Console.WriteLine("This is what was read: " + readIn); //Empty
}
I suggest using image processing methodes to improve the accuracy of tesseract-ocr. I use OpenCV libraries in c++ for this.
So let's take your image and rescale it by +500%:
You can see the image is getting a bit pixely. In this case you want to smooth the edges by using a Gaussian filter. I used a Gaussian filter with a kernal size of 3x3:
The last thing you need to do is segmentation of the digits by using a threshold:
Running tesseract on the segmented image using the digit whitelist will result in "12".
Hope this helped. :)
Hi I have the issue that when I use ScaleTransform(zoomFactor,zoomFactor) the image saved on disk is the original version always, while on screen in the picturebox the image is distorted in proportion to the zoomFactor.
Why this could be happening ? Shouldn't I have the final result as applied from e.Graphics on disk written image ?
My code is the following which is a version with matrix. but the instead of matrix I have used the ScaleTransform as well. Result is always the same:
g=e.Graphics;//inside picturebox_paint()
g.ScaleTransform(ratio * zoomFac, ratio * zoomFac);
e.Graphics.DrawImage((Bitmap)bmp, 0, 0);
int seed = Convert.ToInt32(Regex.Match(Guid.NewGuid().ToString(), #"\d+").Value);
String destinationFile = #"C:\tmp\photoid\" + new Random(seed).Next() + "_conv.jpg";
//Here I get always the original image back!!!!
bmp.Save(destinationFile);
I have used as well the following idiom but with same results:
//Matrix matrix = new Matrix();
//matrix.Scale(zoomFac, zoomFac);
//e.Graphics.Transform = matrix;
You need to make the PictureBox draw the things it shows on screen into a new Bitmap, which you then can save!
As it is the Image will be saved in the original form and nothing you did in the Paint event, which actually painst onto the surface of the PictureBox will be saved.
So to save everything, i.e. The Image, possibly a BackgroundImage and all you draw in the Paint event you would call DrawToBitmap somehwere.
Somewhere means somewhere else, not in the Paint event, as it will call the Paint event to create the new Bitmap, causing an endless loop..
To call it you would do something like this:
Bitmap bmpSave = new Bitmap(pictureBox1.ClientSize.Width, pictureBox1.ClientSize.Height);
pictureBox1.DrawToBitmap(bmpSave, pictureBox1.ClientRectangle);
But maybe this is not really what you want? Maybe you actually want to modify the Image? In that case do not use the Paint event at all!
Instead do something like this:
Bitmap bmpSave = new Bitmap(yourNewWidth, yourNewHeight);
using (Graphics g = Graphics.FromImage(bmpSave))
{
g.ScaleTransform(ratio * zoomFac, ratio * zoomFac);
g.DrawImage((Bitmap)pictureBox1.Image, 0, 0); //
pictureBox1.Image = bmpSave;
bmpSave.Save(...);
}
You could call this from somewhere where the scaling is being triggered from.
Note that doing the scaling repeatedly and each time from the previoulsy scaled version will degrade the quality rather fast. For this always scale from a saved version of the original!!
Btw: Using a Matrix for scaling doesn't really make a difference over ScaleTransform.
But if you want to do a direct scaling why not use the DrawImage overload which takes two Rectangles? This is the most common solution if all you want to to scale and maybe draw other stuff additionally..:
int newWidth = 100; int newHeight = 100; string yourFileName = "D:\\xyz123.jpg";
Bitmap bmpSave = new Bitmap(pictureBox1.ClientSize.Width, pictureBox1.ClientSize.Height);
Rectangle newRectangle = new Rectangle(0, 0, newWidth, newHeight);
Rectangle oldRectangle = new Rectangle(Point.Empty, pictureBox1.Image.Size);
using (Graphics g = Graphics.FromImage(bmpSave))
{
g.DrawImage((Bitmap)pictureBox1.Image, newRectangle, oldRectangle, GraphicsUnit.Pixel);
bmpSave.Save(yourFileName, ImageFormat.Jpeg);
}
And there there is the scaling Bitmap constructor:
Bitmap bmp = new Bitmap(pictureBox1.Image, newWidth, newHeight);
Which I would recommend if all you want is to scale the Image. As the other solutions it will not change the Image displayed until you assign it back into the PictureBox..:
pictureBox1.Image = bmp ;
Don't forget to dispose of the old Image..
Been a while since I messed with GDI but I think you need to copy back to the Bitmap here.
g.DrawImage(bmp, scaledwidth, scaledheight);
Try something like that before bmp.Save
Edit
Apologies for not seeing that you were copying back to the bitmap. Perhaps the overload which specifies the output rectangle is what you need. Try a DrawImage overload which has the destination Rect. https://msdn.microsoft.com/en-us/library/ms142040(v=vs.110).aspx
Since I've tried to draw string with every combination of smoothing and rendering with Graphics.DrawString() I was thinking that text renderer would do a better job drawing my strings but I think was wrong.
This is how it is supposed to look like:
And this is how it looks like:
Here is my code:
Graphics objGraphics2 = Graphics.FromImage(objBitmap);
objGraphics2.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
objGraphics2.TextRenderingHint = System.Drawing.Text.TextRenderingHint.AntiAlias;
objGraphics2.CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.HighQuality;
objGraphics2.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBilinear;
Font textFont = new Font(textFontFamily, PxtoEm(textSize));
SolidBrush b = new SolidBrush(textColor);
TextRenderer.DrawText(objGraphics2, textValue, textFont, new Rectangle(0, 0, Width, Height), textColor);
Is my PxtoEm method wrong?
public float PxtoEm(int px)
{
float em = (float)(Convert.ToDouble(Convert.ToDouble(px) * Convert.ToDouble(72) / Convert.ToDouble(objBitmap.HorizontalResolution)));
return em;
}
I need some suggestions because this is really awful, it gets worse with larger fonts and images aren't shrunk.
UPDATE: Got it working with bigger fonts(ie. 20px) but with smaller fonts it gets kind of erased on some letters:
This is how it's suposed to be with font Arial 10px:
This is result with Graphics.DrawString()
As you can see it really isn't very good but closest I got. I made some changes to code and got better results with larger font:
This is how it's suposed to be with font Arial 20px:
This is drawing result:
And here is the changed code(I droped em method and used pixels directly, switched to Graphics.DrawString() instead of TextRenderer.DrawText()
Graphics objGraphics = Graphics.FromImage(objBitmap);
objGraphics.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
objGraphics.TextRenderingHint = System.Drawing.Text.TextRenderingHint.AntiAliasGridFit;
objGraphics.CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.HighQuality;
objGraphics.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
objGraphics.PixelOffsetMode = System.Drawing.Drawing2D.PixelOffsetMode.HighQuality;
Font textFont = new Font(textFontFamily, textSize,GraphicsUnit.Pixel);
SolidBrush b = new SolidBrush(textColor);
PointF origin = new PointF((float)TextLeft,(float)TextTop);
StringFormat format = StringFormat.GenericTypographic;
objGraphics.DrawString(textValue, textFont, b , origin, format);
If someone has some suggestion to maybe write different method for smaller text sizes and use above code for larger as it works nicely, post it and I'll try it!
UPDATE 3: Finally found solution for everything, and solution was rather simple:
DON'T USE TRANSPARENT BACKGROUND!
And settings are:
objGraphics.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
objGraphics.TextRenderingHint = System.Drawing.Text.TextRenderingHint.ClearTypeGridFit; // <-- important!
objGraphics.CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.HighQuality;
objGraphics.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
objGraphics.PixelOffsetMode = System.Drawing.Drawing2D.PixelOffsetMode.HighQuality;
objGraphics.TextContrast = 0;
Here is final image with these settings on white background:
Exactly the same, thanks for suggestions and replies.
I'm not sure it will help but why not create your font without the function call, like this:
Font textFont = new Font(textFontFamily, textSize, GraphicsUnit.Pixel);
I built something to generate image buttons using similar functionality and I had issues with kerneling and the font not stretching to the desired with. The following settings got me really close to what I wanted but still not 100%.
objGraphics2.PixelOffsetMode = System.Drawing.Drawing2D.PixelOffsetMode.HighQuality;
objGraphics2.TextRenderingHint = System.Drawing.Drawing2D.TextRenderingHint.AntiAliasGridFit;
Set Graphics.TextRenderingHint to SingleBitPerPixelGridFit.
I'm not sure if this will solve the issue, but I had a similar problem with drawing text in Direct3D, check out PixelOffsetMode, set it to Half.
I have a problem with the ListView control in a windows forms application.
Even if I create a thumbnail image or resize the real one I get distorted images in the list view.
The image looks like when you zoom in an image very much.
I first thought that the GetThumbnailImage is couseing this but I used a resize code I found here and I have the same result.
I also did not found any bug related to list view control so I gues I'm doing something wrong but I just can't figure out what.
Here is the code I use:
lsvPictures.LargeImageList = m_imagesList;
lsvPictures.LargeImageList.ImageSize = new Size(100, 100);
lsvPictures.View = View.LargeIcon;
lsvPictures.CheckBoxes = true;
for (int i = 0; i < ofd.FileNames.Length; i++)
{
filename = ofd.FileNames[i].ToString();
ListViewItem lvi = new ListViewItem(filename);
m_imagesList.Images.Add(ResizeImage(Image.FromFile(filename), 100, 100));
lvi.ImageIndex = i;
lsvPictures.Items.Add(lvi);
}
And this is the function that resizes images:
public static System.Drawing.Bitmap ResizeImage(System.Drawing.Image image,
int width, int height)
{
//a holder for the result
Bitmap result = new Bitmap(width, height);
//use a graphics object to draw the resized image into the bitmap
using (Graphics graphics = Graphics.FromImage(result))
{
//set the resize quality modes to high quality
graphics.CompositingQuality =
System.Drawing.Drawing2D.CompositingQuality.HighQuality;
graphics.InterpolationMode =
System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
graphics.SmoothingMode =
System.Drawing.Drawing2D.SmoothingMode.HighQuality;
//draw the image into the target bitmap
graphics.DrawImage(image, 0, 0, result.Width, result.Height);
}
//return the resulting bitmap
return result;
}
Thank you!
Mosu'
I just found the source of the problems:
m_imagesList.ColorDepth = ColorDepth.Depth16Bit;
It seams that, as default, the ColorDepth of the ImageList is 8 bit (or 4 bit, but my guess is 8). If I change this to at least 16 bit everything looks very nice.
To those with similar problems: I changed my Thumbnail method a lot before I realised that the ListView control is not using the color depth the images were having. I put the result of my method on a PictureBox control and saw that the function was working corectly. Atfer this I googled a lot ... and found that silly ColorDepth property.
How did you set the resolution for your image. Also, did what did you set the PixelFormat value to when you created the bitmap? I have a list of images loading into my list view that I am resizing similar to how you are and it is working fine without any distortion in the resulting thumbnail images that are created.
Here is a snippet from my resize method.
Bitmap bitmap = new Bitmap(width, height, PixelFormat.Format24bppRgb);
bitmap.SetResolution(image.HorizontalResolution, image.VerticalResolution);
using (Graphics graphics = Graphics.FromImage(bitmap))
{
graphics.Clear(Color.Red);
graphics.InterpolationMode = InterpolationMode.HighQualityBicubic;
graphics.DrawImage(image,
new Rectangle(destinationX, destinationY, destinationWidth, destinationHeight),
new Rectangle(sourceX, sourceY, originalWidth, originalHeight),
GraphicsUnit.Pixel);
}
return bitmap;
I was also using a ListView in WinForms to display directories, and had the same problem. I suggest that you check the image file type: icon files (.ico) tend to end up distorted, so try to use an image file with the .png extension. This works for me:
ListView listView = new ListView();
ImageList imageList = new ImageList();
// add image to list:
imageList.Images.Add("image_key", image_path);
// give the listview the imagelist:
listView.SmallImageList = imageList;
// add item to listview:
listView.Items.Add("item_text", "image_key");