C TWAIN allows you to customize the scan dimensions in this way.

To solve the problem of customizing scan dimensions using TWAIN in C, follow these steps:

Initialize TWAIN Environment: Use DSM_Init to start the TWAIN environment.
Select and Open Data Source: Enumerate available sources with DS_GetSources, select your scanner, then open it using DS_Open.
Set Custom Dimensions:
Define your desired width and height.
Construct a TW_CUSTOMDSDATA structure with these dimensions.
Use DS_SetDeviceProperty to send this data to the scanner.
Configure Resolution (Optional): Adjust X and Y resolutions using another TW_CUSTOMDSDATA if needed.
Initiate Scan: Call MSG_ScanImage to start scanning.
Handle Image Data and Cleanup: Retrieve image data, then properly close the source with DS_Close and clean up resources.

Here’s an example implementation:

#include <stdio.h>
#include “twain.h”

int main() {
    // Initialize TWAIN environment
    DSM_Init();

    // Enumerate sources
    LONG hds = 0;
    if (DS_GetSources(&hds) != SUCCESS) {
        printf(“Failed to get sources\n”);
        return -1;
    }

    // Select and open source (scanner)
    LONG hwnd = 0; // Application window handle
    LONG hsrc = 0;
    if (DS_Open(hwnd, &hsrc, “Source Name”) != SUCCESS) {
        printf(“Failed to open source\n”);
        return -1;
    }

    // Set custom dimensions
    TW_CUSTOMDSDATA data;
    memset(&data, 0, sizeof(data));
    data.Size = sizeof(TW_CUSTOMDSDATA);
    data.Type = TW_DSTYPE_IMAGECAPABILITY;

    data.Data.Image.Capability.Version.major = 2;
    data.Data.Image.Capability.Version.minor = 1;
    data.Data.Image.Capability.Frame.left = 0;      // Left offset
    data.Data.Image.Capability.Frame.top = 0;       // Top offset
    data.Data.Image.Capability.Frame.right = 800;   // Width
    data.Data.Image.Capability.Frame.bottom = 600;  // Height

    if (DS_SetDeviceProperty(hsrc, &data) != SUCCESS) {
        printf(“Failed to set dimensions\n”);
        return -1;
    }

    // Set resolution (optional)
    data.Type = TW_DSTYPE_INT32;
    data.Data.Int = 300; // DPI
    if (DS_SetDeviceProperty(hsrc, &data) != SUCCESS) {
        printf(“Failed to set resolution\n”);
        return -1;
    }

    // Start scan
    if (DSM_Entry(hsrc, hwnd, hwnd, MSG_ScanImage) != SUCCESS) {
        printf(“Scan failed\n”);
        return -1;
    }

    // Process scanned image…

    // Cleanup
    DS_Close(hsrc);
    DSM_Exit();

    return 0;
}

#include <stdio.h>

#include “twain.h”

int main() {

// Initialize TWAIN environment

DSM_Init();

// Enumerate sources

LONG hds = 0;

if (DS_GetSources(&hds) != SUCCESS) {

printf(“Failed to get sources\n”);

return –1;

}

// Select and open source (scanner)

LONG hwnd = 0; // Application window handle

LONG hsrc = 0;

if (DS_Open(hwnd, &hsrc, “Source Name”) != SUCCESS) {

printf(“Failed to open source\n”);

return –1;

}

// Set custom dimensions

TW_CUSTOMDSDATA data;

memset(&data, 0, sizeof(data));

data.Size = sizeof(TW_CUSTOMDSDATA);

data.Type = TW_DSTYPE_IMAGECAPABILITY;

data.Data.Image.Capability.Version.major = 2;

data.Data.Image.Capability.Version.minor = 1;

data.Data.Image.Capability.Frame.left = 0; // Left offset

data.Data.Image.Capability.Frame.top = 0; // Top offset

data.Data.Image.Capability.Frame.right = 800; // Width

data.Data.Image.Capability.Frame.bottom = 600; // Height

if (DS_SetDeviceProperty(hsrc, &data) != SUCCESS) {

printf(“Failed to set dimensions\n”);

return –1;

}

// Set resolution (optional)

data.Type = TW_DSTYPE_INT32;

data.Data.Int = 300; // DPI

if (DS_SetDeviceProperty(hsrc, &data) != SUCCESS) {

printf(“Failed to set resolution\n”);

return –1;

}

// Start scan

if (DSM_Entry(hsrc, hwnd, hwnd, MSG_ScanImage) != SUCCESS) {

printf(“Scan failed\n”);

return –1;

}

// Process scanned image…

// Cleanup

DS_Close(hsrc);

DSM_Exit();

return 0;

}

This code initializes TWAIN, configures custom scan dimensions and resolution, initiates a scan, and cleans up properly. Adjust the left, top, right, and bottom values to your desired scan area.