How can I resize the Tiff Image without compromising its quality?

[Nanthini]

I used PyQt6 (Qt Creator) Graphics View to display a TIFF document in my Image Viewer Project.
The original size of the TIFF document was 2550x3300 pixels. The document became pixelated when I reduced its size to 800x900 pixels, making it difficult to read tables and text due to reduced quality.
How can I resize the document and load the image in graphics view without compromising its quality?

[qwasder85]

@Nanthini If you're showing your TIF in a QPixmap, you can use the QPixmap::scaled()-function and pass Qt::SmoothTransformation for the transform mode. This does soften the look of it a bit, though.

[Nanthini]

@qwasder85 Here I mention my sample code

def load_tif_image(self, file_path):
    if file_path:
        gray_img = cv2.imread(file_path, cv2.IMREAD_GRAYSCALE)  # grayscale
        if gray_img is not None:
            original_height, original_width = gray_img.shape
            aspect_ratio = original_width / original_height
            a4_width_mm = 210
            a4_height_mm = 297
            dpi = 300
            a4_width_pixels = int(a4_width_mm * dpi / 76.3) # 25.4 mm = 1 inch 76.3 mm = 3inch
            a4_height_pixels = int(a4_height_mm * dpi / 101.6) #25.4 mm = 1 inch 101.6 mm = 4inch
            if aspect_ratio > 1:
                new_width = a4_width_pixels
                new_height = int(new_width / aspect_ratio)
            else:
                new_height = a4_height_pixels
                new_width = int(new_height * aspect_ratio)
            resized_img = cv2.resize(gray_img, (new_width, new_height), interpolation=cv2.INTER_LANCZOS4)
            bytes_per_line = 0.1 * new_width  # 1 byte per pixel for grayscale
            q_img = QImage(resized_img.data, new_width, new_height, bytes_per_line, QImage.Format.Format_Grayscale16)
            pixmap = QPixmap.fromImage(q_img)
            self.grphics_scene.clear()
            pixmap_item = QGraphicsPixmapItem(pixmap)
            self.graphics_scene.addItem(pixmap_item)
            self.graphics_view.setScene(self.scene)
            self.graphics_view.setRenderHint(QPainter.RenderHint.Antialiasing)
            self.graphics_view.setRenderHint(QPainter.RenderHint.SmoothPixmapTransform)

[qwasder85]

@Nanthini At your line

pixmap = QPixmap.fromImage(q_img)

you should be able to do all the resizing and transforming like this:

pixmap = QPixmap.fromImage(q_img).scaled(yourNewWidth, yourNewHeight, transformMode=QtCore.Qt.SmoothTransformation)

Not a Python guy, but it should work similarly to this.

[Nanthini]

@qwasder85 I'm grateful for the solution you shared; it worked perfectly. Thank you!